{
  "title": "Surface Area of Cube - Grade 9 CBSE",
  "total_questions": 100,
  "questions": [
    {"id": 1, "difficulty": "easy", "question": "What is the surface area of a cube with side length 2 cm?", "options": {"A": "20 cm²", "B": "24 cm²", "C": "16 cm²", "D": "12 cm²"}, "correct_answer": "B"},
    {"id": 2, "difficulty": "easy", "question": "If the side of a cube is 3 m, what is its total surface area?", "options": {"A": "54 m²", "B": "36 m²", "C": "27 m²", "D": "48 m²"}, "correct_answer": "A"},
    {"id": 3, "difficulty": "easy", "question": "The surface area of a cube is 96 cm². What is the length of one side?", "options": {"A": "5 cm", "B": "6 cm", "C": "4 cm", "D": "3 cm"}, "correct_answer": "C"},
    {"id": 4, "difficulty": "easy", "question": "A cube has side length 5 cm. What is the area of one face?", "options": {"A": "30 cm²", "B": "25 cm²", "C": "20 cm²", "D": "15 cm²"}, "correct_answer": "B"},
    {"id": 5, "difficulty": "easy", "question": "What is the surface area of a cube with edge length 1.5 m?", "options": {"A": "12.5 m²", "B": "13.5 m²", "C": "14.5 m²", "D": "15.5 m²"}, "correct_answer": "B"},
    {"id": 6, "difficulty": "easy", "question": "How many faces does a cube have?", "options": {"A": "4", "B": "5", "C": "6", "D": "8"}, "correct_answer": "C"},
    {"id": 7, "difficulty": "easy", "question": "If each edge of a cube is doubled, how many times does the surface area increase?", "options": {"A": "2 times", "B": "3 times", "C": "4 times", "D": "8 times"}, "correct_answer": "C"},
    {"id": 8, "difficulty": "easy", "question": "What is the formula for total surface area of a cube?", "options": {"A": "4a²", "B": "5a²", "C": "6a²", "D": "3a²"}, "correct_answer": "C"},
    {"id": 9, "difficulty": "easy", "question": "A cube has surface area 150 cm². What is the area of one face?", "options": {"A": "20 cm²", "B": "25 cm²", "C": "30 cm²", "D": "35 cm²"}, "correct_answer": "B"},
    {"id": 10, "difficulty": "easy", "question": "The side of a cube is 0.5 m. What is its surface area in square meters?", "options": {"A": "1 m²", "B": "1.5 m²", "C": "2 m²", "D": "2.5 m²"}, "correct_answer": "B"},
    {"id": 11, "difficulty": "easy", "question": "If a cube has side length 7 cm, what is its surface area?", "options": {"A": "284 cm²", "B": "294 cm²", "C": "304 cm²", "D": "314 cm²"}, "correct_answer": "B"},
    {"id": 12, "difficulty": "easy", "question": "What is the surface area of a cube with side 10 mm?", "options": {"A": "600 mm²", "B": "500 mm²", "C": "400 mm²", "D": "300 mm²"}, "correct_answer": "A"},
    {"id": 13, "difficulty": "easy", "question": "A cube has edge length 2.5 cm. Calculate its surface area.", "options": {"A": "35.5 cm²", "B": "36.5 cm²", "C": "37.5 cm²", "D": "38.5 cm²"}, "correct_answer": "C"},
    {"id": 14, "difficulty": "easy", "question": "The surface area of a cube is 54 m². Find its side length.", "options": {"A": "2 m", "B": "2.5 m", "C": "3 m", "D": "3.5 m"}, "correct_answer": "C"},
    {"id": 15, "difficulty": "easy", "question": "What is the perimeter of one face of a cube with side 4 cm?", "options": {"A": "12 cm", "B": "14 cm", "C": "16 cm", "D": "18 cm"}, "correct_answer": "C"},
    {"id": 16, "difficulty": "easy", "question": "If a cube's side increases from 2 cm to 4 cm, by how much does surface area increase?", "options": {"A": "48 cm²", "B": "72 cm²", "C": "96 cm²", "D": "120 cm²"}, "correct_answer": "B"},
    {"id": 17, "difficulty": "easy", "question": "A cube has surface area 600 cm². What is its side length?", "options": {"A": "8 cm", "B": "9 cm", "C": "10 cm", "D": "11 cm"}, "correct_answer": "C"},
    {"id": 18, "difficulty": "easy", "question": "What is the ratio of surface areas of two cubes with sides 2 cm and 4 cm?", "options": {"A": "1:2", "B": "1:4", "C": "1:6", "D": "1:8"}, "correct_answer": "B"},
    {"id": 19, "difficulty": "easy", "question": "The edge of a cube is 6 dm. What is its surface area in dm²?", "options": {"A": "196 dm²", "B": "206 dm²", "C": "216 dm²", "D": "226 dm²"}, "correct_answer": "C"},
    {"id": 20, "difficulty": "easy", "question": "A cube has side 1.2 m. Find its surface area.", "options": {"A": "8.64 m²", "B": "9.64 m²", "C": "10.64 m²", "D": "11.64 m²"}, "correct_answer": "A"},
    {"id": 21, "difficulty": "medium", "question": "Three cubes of side 2 cm each are joined end to end. What is the surface area of the resulting cuboid?", "options": {"A": "56 cm²", "B": "64 cm²", "C": "72 cm²", "D": "80 cm²"}, "correct_answer": "A"},
    {"id": 22, "difficulty": "medium", "question": "A cube of side 8 cm is cut into smaller cubes of side 2 cm each. What is the ratio of total surface area of all smaller cubes to original cube?", "options": {"A": "1:1", "B": "2:1", "C": "3:1", "D": "4:1"}, "correct_answer": "D"},
    {"id": 23, "difficulty": "medium", "question": "If the surface area of a cube is 486 cm², find its volume.", "options": {"A": "729 cm³", "B": "512 cm³", "C": "343 cm³", "D": "216 cm³"}, "correct_answer": "A"},
    {"id": 24, "difficulty": "medium", "question": "The diagonal of a cube is 6√3 cm. What is its surface area?", "options": {"A": "144 cm²", "B": "196 cm²", "C": "216 cm²", "D": "256 cm²"}, "correct_answer": "C"},
    {"id": 25, "difficulty": "medium", "question": "A cube has surface area 384 m². What is the length of its diagonal?", "options": {"A": "8√3 m", "B": "10√3 m", "C": "12√3 m", "D": "14√3 m"}, "correct_answer": "A"},
    {"id": 26, "difficulty": "medium", "question": "The volume of a cube is 512 cm³. What is its surface area?", "options": {"A": "384 cm²", "B": "424 cm²", "C": "464 cm²", "D": "504 cm²"}, "correct_answer": "A"},
    {"id": 27, "difficulty": "medium", "question": "If each edge of a cube increases by 50%, by what percentage does surface area increase?", "options": {"A": "100%", "B": "125%", "C": "150%", "D": "175%"}, "correct_answer": "B"},
    {"id": 28, "difficulty": "medium", "question": "A cube is painted on all faces and cut into 64 smaller cubes of equal size. How many small cubes have exactly 2 faces painted?", "options": {"A": "16", "B": "24", "C": "32", "D": "48"}, "correct_answer": "B"},
    {"id": 29, "difficulty": "medium", "question": "The ratio of surface areas of two cubes is 9:25. What is the ratio of their volumes?", "options": {"A": "3:5", "B": "9:25", "C": "27:125", "D": "81:625"}, "correct_answer": "C"},
    {"id": 30, "difficulty": "medium", "question": "A cube of side 10 cm has a square hole of side 4 cm cut through it. What is the surface area of remaining solid?", "options": {"A": "792 cm²", "B": "832 cm²", "C": "872 cm²", "D": "912 cm²"}, "correct_answer": "A"},
    {"id": 31, "difficulty": "medium", "question": "The surface area of a cube is 1014 cm². Find its edge length.", "options": {"A": "11 cm", "B": "12 cm", "C": "13 cm", "D": "14 cm"}, "correct_answer": "C"},
    {"id": 32, "difficulty": "medium", "question": "Two cubes have volumes in ratio 8:27. What is ratio of their surface areas?", "options": {"A": "2:3", "B": "4:9", "C": "8:27", "D": "16:81"}, "correct_answer": "B"},
    {"id": 33, "difficulty": "medium", "question": "A cube has diagonal of face 10√2 cm. What is its surface area?", "options": {"A": "400 cm²", "B": "500 cm²", "C": "600 cm²", "D": "700 cm²"}, "correct_answer": "C"},
    {"id": 34, "difficulty": "medium", "question": "If surface area of cube increases by 69%, by what percentage does edge increase?", "options": {"A": "20%", "B": "25%", "C": "30%", "D": "35%"}, "correct_answer": "C"},
    {"id": 35, "difficulty": "medium", "question": "A cubical box of edge 20 cm is open at top. What is its surface area?", "options": {"A": "2000 cm²", "B": "2200 cm²", "C": "2400 cm²", "D": "2600 cm²"}, "correct_answer": "A"},
    {"id": 36, "difficulty": "medium", "question": "The cost of painting a cubical box at ₹5 per m² is ₹750. What is edge length of cube?", "options": {"A": "4 m", "B": "5 m", "C": "6 m", "D": "7 m"}, "correct_answer": "B"},
    {"id": 37, "difficulty": "medium", "question": "A cube of side 'a' has same surface area as sphere of radius 'r'. If a=7 cm, find r.", "options": {"A": "4.83 cm", "B": "5.43 cm", "C": "6.03 cm", "D": "6.63 cm"}, "correct_answer": "A"},
    {"id": 38, "difficulty": "medium", "question": "Four cubes of side 3 cm each are joined to form a cuboid. What is surface area of cuboid?", "options": {"A": "144 cm²", "B": "162 cm²", "C": "180 cm²", "D": "198 cm²"}, "correct_answer": "B"},
    {"id": 39, "difficulty": "medium", "question": "The lateral surface area of cube is 144 cm². What is its total surface area?", "options": {"A": "180 cm²", "B": "196 cm²", "C": "216 cm²", "D": "240 cm²"}, "correct_answer": "C"},
    {"id": 40, "difficulty": "medium", "question": "A cube has surface area 1350 cm². What is diagonal of cube?", "options": {"A": "15√3 cm", "B": "18√3 cm", "C": "21√3 cm", "D": "24√3 cm"}, "correct_answer": "A"},
    {"id": 41, "difficulty": "hard", "question": "A cube of side 12 cm has a square pyramid of side 12 cm and height 6 cm placed on top. What is total surface area of combined solid?", "options": {"A": "1152 cm²", "B": "1296 cm²", "C": "1440 cm²", "D": "1584 cm²"}, "correct_answer": "B"},
    {"id": 42, "difficulty": "hard", "question": "A cubical block of side 7 cm is surmounted by hemisphere of diameter 7 cm. Find surface area of solid.", "options": {"A": "332.5 cm²", "B": "346.5 cm²", "C": "360.5 cm²", "D": "374.5 cm²"}, "correct_answer": "B"},
    {"id": 43, "difficulty": "hard", "question": "The surface area of cube is 54x². If each edge is increased by 100%, new surface area is?", "options": {"A": "108x²", "B": "162x²", "C": "216x²", "D": "270x²"}, "correct_answer": "C"},
    {"id": 44, "difficulty": "hard", "question": "A cube of metal of edge 12 cm is melted and recast into 8 smaller cubes of equal size. What is surface area of each small cube?", "options": {"A": "144 cm²", "B": "216 cm²", "C": "288 cm²", "D": "324 cm²"}, "correct_answer": "B"},
    {"id": 45, "difficulty": "hard", "question": "From a solid cube of side 7 cm, a conical cavity of radius 3.5 cm and height 7 cm is drilled out. Find surface area of remaining solid.", "options": {"A": "294 cm²", "B": "308 cm²", "C": "322 cm²", "D": "336 cm²"}, "correct_answer": "C"},
    {"id": 46, "difficulty": "hard", "question": "The ratio of surface areas of two cubes is 1:4. If volume of smaller cube is 125 cm³, what is edge of larger cube?", "options": {"A": "8 cm", "B": "9 cm", "C": "10 cm", "D": "12 cm"}, "correct_answer": "C"},
    {"id": 47, "difficulty": "hard", "question": "A cube of side 10 cm is painted and cut into 1000 cubes of 1 cm each. How many cubes have exactly one face painted?", "options": {"A": "384", "B": "486", "C": "512", "D": "648"}, "correct_answer": "A"},
    {"id": 48, "difficulty": "hard", "question": "If diagonal of cube is √300 cm, what is its surface area?", "options": {"A": "300 cm²", "B": "400 cm²", "C": "500 cm²", "D": "600 cm²"}, "correct_answer": "D"},
    {"id": 49, "difficulty": "hard", "question": "Three cubes of sides 3 cm, 4 cm and 5 cm are melted to form one cube. Find surface area of new cube.", "options": {"A": "216 cm²", "B": "294 cm²", "C": "384 cm²", "D": "486 cm²"}, "correct_answer": "D"},
    {"id": 50, "difficulty": "hard", "question": "A cubical tank of edge 2 m is filled with water. If water is transferred to smaller cubes of edge 0.5 m, how many small cubes can be filled?", "options": {"A": "32", "B": "48", "C": "64", "D": "128"}, "correct_answer": "C"},
    {"id": 51, "difficulty": "medium", "question": "A cube has surface area 726 cm². What is its volume?", "options": {"A": "1331 cm³", "B": "1728 cm³", "C": "2197 cm³", "D": "2744 cm³"}, "correct_answer": "A"},
    {"id": 52, "difficulty": "medium", "question": "The edge of cube is increased by 20%. By what percent does surface area increase?", "options": {"A": "40%", "B": "44%", "C": "48%", "D": "52%"}, "correct_answer": "B"},
    {"id": 53, "difficulty": "medium", "question": "A cube has diagonal of length 10√3 cm. Find its surface area.", "options": {"A": "400 cm²", "B": "500 cm²", "C": "600 cm²", "D": "700 cm²"}, "correct_answer": "C"},
    {"id": 54, "difficulty": "medium", "question": "If surface area of cube is 864 cm², find length of its diagonal.", "options": {"A": "12√3 cm", "B": "14√3 cm", "C": "16√3 cm", "D": "18√3 cm"}, "correct_answer": "A"},
    {"id": 55, "difficulty": "medium", "question": "The ratio of volumes of two cubes is 64:125. What is ratio of their surface areas?", "options": {"A": "4:5", "B": "8:15", "C": "16:25", "D": "64:125"}, "correct_answer": "C"},
    {"id": 56, "difficulty": "medium", "question": "A cube of side 6 cm is cut into smaller cubes of side 2 cm. What is total surface area of all small cubes?", "options": {"A": "432 cm²", "B": "648 cm²", "C": "864 cm²", "D": "972 cm²"}, "correct_answer": "B"},
    {"id": 57, "difficulty": "medium", "question": "The lateral surface area of cube is 256 cm². Find its total surface area.", "options": {"A": "384 cm²", "B": "400 cm²", "C": "416 cm²", "D": "432 cm²"}, "correct_answer": "A"},
    {"id": 58, "difficulty": "medium", "question": "A cubical box without lid has surface area 500 cm². What is edge length?", "options": {"A": "8 cm", "B": "9 cm", "C": "10 cm", "D": "11 cm"}, "correct_answer": "C"},
    {"id": 59, "difficulty": "medium", "question": "If edge of cube is tripled, surface area becomes how many times?", "options": {"A": "3 times", "B": "6 times", "C": "9 times", "D": "12 times"}, "correct_answer": "C"},
    {"id": 60, "difficulty": "medium", "question": "A cube has surface area 1176 cm². What is area of one face?", "options": {"A": "144 cm²", "B": "169 cm²", "C": "196 cm²", "D": "225 cm²"}, "correct_answer": "C"},
    {"id": 61, "difficulty": "medium", "question": "The surface area of cube is 150% of its lateral surface area. What is edge length if lateral surface area is 100 cm²?", "options": {"A": "4 cm", "B": "5 cm", "C": "6 cm", "D": "7 cm"}, "correct_answer": "B"},
    {"id": 62, "difficulty": "medium", "question": "A cube of side 8 cm is painted blue and cut into 512 cubes of 1 cm each. How many cubes have 3 blue faces?", "options": {"A": "4", "B": "6", "C": "8", "D": "12"}, "correct_answer": "C"},
    {"id": 63, "difficulty": "medium", "question": "If diagonal of cube is 12 cm, find its surface area.", "options": {"A": "288 cm²", "B": "324 cm²", "C": "384 cm²", "D": "432 cm²"}, "correct_answer": "A"},
    {"id": 64, "difficulty": "medium", "question": "Two cubes have edges in ratio 3:4. What is ratio of their surface areas?", "options": {"A": "9:16", "B": "27:64", "C": "3:4", "D": "6:8"}, "correct_answer": "A"},
    {"id": 65, "difficulty": "medium", "question": "A cube has volume 4913 cm³. What is its surface area?", "options": {"A": "1734 cm²", "B": "1849 cm²", "C": "1964 cm²", "D": "2079 cm²"}, "correct_answer": "A"},
    {"id": 66, "difficulty": "medium", "question": "The cost of painting a cube at ₹2.50 per cm² is ₹600. What is volume of cube?", "options": {"A": "64 cm³", "B": "125 cm³", "C": "216 cm³", "D": "343 cm³"}, "correct_answer": "C"},
    {"id": 67, "difficulty": "medium", "question": "If surface area increases from 54 cm² to 96 cm², by what factor does edge increase?", "options": {"A": "1.2", "B": "1.33", "C": "1.5", "D": "1.67"}, "correct_answer": "B"},
    {"id": 68, "difficulty": "medium", "question": "A cube has diagonal of face 14√2 cm. Find its surface area.", "options": {"A": "1176 cm²", "B": "1296 cm²", "C": "1416 cm²", "D": "1536 cm²"}, "correct_answer": "A"},
    {"id": 69, "difficulty": "medium", "question": "The surface area of cube is 4 times area of one face. What is edge length if one face area is 36 cm²?", "options": {"A": "6 cm", "B": "8 cm", "C": "10 cm", "D": "12 cm"}, "correct_answer": "A"},
    {"id": 70, "difficulty": "medium", "question": "A cubical tank open at top has surface area 245 m². What is its edge?", "options": {"A": "5 m", "B": "6 m", "C": "7 m", "D": "8 m"}, "correct_answer": "C"},
    {"id": 71, "difficulty": "hard", "question": "A solid cube of side 14 cm is cut into 8 cubes of equal volume. What is surface area of each small cube?", "options": {"A": "294 cm²", "B": "336 cm²", "C": "384 cm²", "D": "432 cm²"}, "correct_answer": "A"},
    {"id": 72, "difficulty": "hard", "question": "A cube of side 10 cm has cylindrical hole of radius 2 cm drilled through it. Find surface area of remaining solid.", "options": {"A": "600 + 80π cm²", "B": "600 + 120π cm²", "C": "600 + 160π cm²", "D": "600 + 200π cm²"}, "correct_answer": "A"},
    {"id": 73, "difficulty": "hard", "question": "The surface area of cube is numerically equal to its volume. What is edge length?", "options": {"A": "4 units", "B": "5 units", "C": "6 units", "D": "7 units"}, "correct_answer": "C"},
    {"id": 74, "difficulty": "hard", "question": "A cube of side 12 cm is cut into 216 equal cubes. What is total surface area of all small cubes?", "options": {"A": "5184 cm²", "B": "7776 cm²", "C": "10368 cm²", "D": "15552 cm²"}, "correct_answer": "C"},
    {"id": 75, "difficulty": "hard", "question": "If edge of cube is increased by 10%, then decreased by 10%, what is net change in surface area?", "options": {"A": "decrease by 1%", "B": "increase by 1%", "C": "decrease by 2%", "D": "increase by 2%"}, "correct_answer": "A"},
    {"id": 76, "difficulty": "hard", "question": "A cube has surface area S and volume V. If S = 6V^(2/3), what is edge length?", "options": {"A": "1 unit", "B": "2 units", "C": "3 units", "D": "4 units"}, "correct_answer": "A"},
    {"id": 77, "difficulty": "hard", "question": "The diagonal of cube is 15√3 cm. Find area of cross-section through vertices not on same face.", "options": {"A": "225√2 cm²", "B": "225√3 cm²", "C": "450 cm²", "D": "450√2 cm²"}, "correct_answer": "A"},
    {"id": 78, "difficulty": "hard", "question": "A cube of side 8 cm is painted and cut into 1 cm cubes. How many cubes have no face painted?", "options": {"A": "216", "B": "256", "C": "294", "D": "343"}, "correct_answer": "A"},
    {"id": 79, "difficulty": "hard", "question": "The ratio of surface areas of cube to sphere is 2:3. If cube edge is 14 cm, find sphere radius.", "options": {"A": "7 cm", "B": "8 cm", "C": "9 cm", "D": "10 cm"}, "correct_answer": "A"},
    {"id": 80, "difficulty": "hard", "question": "A cube has surface area 96a². If each edge is halved, new surface area is?", "options": {"A": "12a²", "B": "24a²", "C": "36a²", "D": "48a²"}, "correct_answer": "B"},
    {"id": 81, "difficulty": "easy", "question": "What is surface area of cube with side 0.8 m?", "options": {"A": "3.84 m²", "B": "4.84 m²", "C": "5.84 m²", "D": "6.84 m²"}, "correct_answer": "A"},
    {"id": 82, "difficulty": "easy", "question": "A cube has edge 15 cm. What is area of one face in cm²?", "options": {"A": "150", "B": "175", "C": "200", "D": "225"}, "correct_answer": "D"},
    {"id": 83, "difficulty": "easy", "question": "If side of cube is 2.2 m, surface area is?", "options": {"A": "28.04 m²", "B": "29.04 m²", "C": "30.04 m²", "D": "31.04 m²"}, "correct_answer": "B"},
    {"id": 84, "difficulty": "easy", "question": "Surface area of cube is 150 cm². Edge length is?", "options": {"A": "4 cm", "B": "5 cm", "C": "6 cm", "D": "7 cm"}, "correct_answer": "B"},
    {"id": 85, "difficulty": "easy", "question": "Cube with side 9 dm has surface area?", "options": {"A": "486 dm²", "B": "496 dm²", "C": "506 dm²", "D": "516 dm²"}, "correct_answer": "A"},
    {"id": 86, "difficulty": "medium", "question": "Two cubes have edges 5 cm and 10 cm. What is ratio of their surface areas?", "options": {"A": "1:2", "B": "1:3", "C": "1:4", "D": "1:5"}, "correct_answer": "C"},
    {"id": 87, "difficulty": "medium", "question": "If edge increases by 25%, surface area increases by?", "options": {"A": "50%", "B": "56.25%", "C": "62.5%", "D": "75%"}, "correct_answer": "B"},
    {"id": 88, "difficulty": "medium", "question": "Cube volume is 343 cm³. Surface area is?", "options": {"A": "264 cm²", "B": "284 cm²", "C": "294 cm²", "D": "304 cm²"}, "correct_answer": "C"},
    {"id": 89, "difficulty": "medium", "question": "Diagonal of cube face is 10 cm. Surface area is?", "options": {"A": "200 cm²", "B": "300 cm²", "C": "400 cm²", "D": "500 cm²"}, "correct_answer": "B"},
    {"id": 90, "difficulty": "hard", "question": "Cube surface area is 216 cm². What is longest diagonal?", "options": {"A": "6√3 cm", "B": "8√3 cm", "C": "10√3 cm", "D": "12√3 cm"}, "correct_answer": "A"},
    {"id": 91, "difficulty": "hard", "question": "Three cubes of sides 6, 8, 10 cm are melted to form one cube. New surface area?", "options": {"A": "864 cm²", "B": "1176 cm²", "C": "1296 cm²", "D": "1536 cm²"}, "correct_answer": "B"},
    {"id": 92, "difficulty": "easy", "question": "Cube side is 11 cm. Surface area?", "options": {"A": "726 cm²", "B": "736 cm²", "C": "746 cm²", "D": "756 cm²"}, "correct_answer": "A"},
    {"id": 93, "difficulty": "easy", "question": "Surface area 2400 cm². Edge?", "options": {"A": "18 cm", "B": "19 cm", "C": "20 cm", "D": "21 cm"}, "correct_answer": "C"},
    {"id": 94, "difficulty": "medium", "question": "Edge increases from 4 to 6 cm. Surface area increase?", "options": {"A": "52 cm²", "B": "104 cm²", "C": "156 cm²", "D": "208 cm²"}, "correct_answer": "B"},
    {"id": 95, "difficulty": "medium", "question": "Cube painted and cut into 27 cubes. How many have 2 faces painted?", "options": {"A": "8", "B": "10", "C": "12", "D": "14"}, "correct_answer": "C"},
    {"id": 96, "difficulty": "hard", "question": "Cube has surface area equal to volume. Edge?", "options": {"A": "4", "B": "5", "C": "6", "D": "7"}, "correct_answer": "C"},
    {"id": 97, "difficulty": "hard", "question": "Cube diagonal 20√3 cm. Surface area?", "options": {"A": "2400 cm²", "B": "2600 cm²", "C": "2800 cm²", "D": "3000 cm²"}, "correct_answer": "A"},
    {"id": 98, "difficulty": "easy", "question": "Side 1.5 m. Surface area?", "options": {"A": "13.5 m²", "B": "14.5 m²", "C": "15.5 m²", "D": "16.5 m²"}, "correct_answer": "A"},
    {"id": 99, "difficulty": "easy", "question": "Surface area formula?", "options": {"A": "a³", "B": "4a²", "C": "5a²", "D": "6a²"}, "correct_answer": "D"},
    {"id": 100, "difficulty": "medium", "question": "Cube volume 1000 cm³. Surface area?", "options": {"A": "500 cm²", "B": "550 cm²", "C": "600 cm²", "D": "650 cm²"}, "correct_answer": "C"}
  ]
}