{
  "title": "Surface Area of Cuboid - Grade 9 CBSE",
  "total_questions": 100,
  "questions": [
    {"id": 1, "difficulty": "easy", "question": "What is the surface area of a cuboid with length 3 cm, breadth 2 cm, and height 1 cm?", "options": {"A": "22 cm²", "B": "24 cm²", "C": "26 cm²", "D": "28 cm²"}, "correct_answer": "A"},
    {"id": 2, "difficulty": "easy", "question": "A cuboid has dimensions 5 m × 4 m × 3 m. What is its total surface area?", "options": {"A": "94 m²", "B": "96 m²", "C": "98 m²", "D": "100 m²"}, "correct_answer": "A"},
    {"id": 3, "difficulty": "easy", "question": "What is the lateral surface area of a cuboid with length 6 cm, width 4 cm, and height 5 cm?", "options": {"A": "80 cm²", "B": "90 cm²", "C": "100 cm²", "D": "110 cm²"}, "correct_answer": "C"},
    {"id": 4, "difficulty": "easy", "question": "If length = 8 cm, breadth = 6 cm, height = 4 cm, what is total surface area?", "options": {"A": "208 cm²", "B": "218 cm²", "C": "228 cm²", "D": "238 cm²"}, "correct_answer": "A"},
    {"id": 5, "difficulty": "easy", "question": "A cuboid has dimensions 10 cm × 8 cm × 5 cm. What is area of its base?", "options": {"A": "40 cm²", "B": "50 cm²", "C": "80 cm²", "D": "100 cm²"}, "correct_answer": "C"},
    {"id": 6, "difficulty": "easy", "question": "What is the formula for total surface area of cuboid?", "options": {"A": "lb + bh + hl", "B": "2(lb + bh + hl)", "C": "l + b + h", "D": "lbh"}, "correct_answer": "B"},
    {"id": 7, "difficulty": "easy", "question": "A cuboid has length 12 m, width 7 m, height 5 m. Find surface area.", "options": {"A": "358 m²", "B": "368 m²", "C": "378 m²", "D": "388 m²"}, "correct_answer": "A"},
    {"id": 8, "difficulty": "easy", "question": "What is lateral surface area formula for cuboid?", "options": {"A": "2(l + b)h", "B": "2(lb + bh)", "C": "2h(l + b)", "D": "lb + bh"}, "correct_answer": "C"},
    {"id": 9, "difficulty": "easy", "question": "Cuboid dimensions: 2.5 m × 2 m × 1.5 m. Surface area?", "options": {"A": "23.5 m²", "B": "24.5 m²", "C": "25.5 m²", "D": "26.5 m²"}, "correct_answer": "A"},
    {"id": 10, "difficulty": "easy", "question": "If l=9 cm, b=6 cm, h=3 cm, what is lateral surface area?", "options": {"A": "80 cm²", "B": "85 cm²", "C": "90 cm²", "D": "95 cm²"}, "correct_answer": "C"},
    {"id": 11, "difficulty": "easy", "question": "A cuboid has surface area 94 cm². If l=5 cm, b=4 cm, find h.", "options": {"A": "2 cm", "B": "2.5 cm", "C": "3 cm", "D": "3.5 cm"}, "correct_answer": "C"},
    {"id": 12, "difficulty": "easy", "question": "What is surface area of cube which is special cuboid with l=b=h=7 cm?", "options": {"A": "284 cm²", "B": "294 cm²", "C": "304 cm²", "D": "314 cm²"}, "correct_answer": "B"},
    {"id": 13, "difficulty": "easy", "question": "Cuboid: l=15 dm, b=10 dm, h=8 dm. Surface area in dm²?", "options": {"A": "600 dm²", "B": "650 dm²", "C": "700 dm²", "D": "750 dm²"}, "correct_answer": "C"},
    {"id": 14, "difficulty": "easy", "question": "If surface area = 376 cm², l=10 cm, b=8 cm, find h.", "options": {"A": "4 cm", "B": "5 cm", "C": "6 cm", "D": "7 cm"}, "correct_answer": "C"},
    {"id": 15, "difficulty": "easy", "question": "A cuboid open at top has dimensions 6×5×4 cm. What is surface area?", "options": {"A": "118 cm²", "B": "128 cm²", "C": "138 cm²", "D": "148 cm²"}, "correct_answer": "B"},
    {"id": 16, "difficulty": "easy", "question": "Which is not a face of cuboid?", "options": {"A": "Rectangle", "B": "Square", "C": "Circle", "D": "All can be faces"}, "correct_answer": "C"},
    {"id": 17, "difficulty": "easy", "question": "l=2.2 m, b=1.8 m, h=1.5 m. Surface area?", "options": {"A": "17.52 m²", "B": "18.72 m²", "C": "19.92 m²", "D": "21.12 m²"}, "correct_answer": "B"},
    {"id": 18, "difficulty": "easy", "question": "Cuboid with l:b:h = 3:2:1. If l=9 cm, surface area?", "options": {"A": "198 cm²", "B": "208 cm²", "C": "218 cm²", "D": "228 cm²"}, "correct_answer": "A"},
    {"id": 19, "difficulty": "easy", "question": "How many pairs of identical faces in cuboid?", "options": {"A": "2", "B": "3", "C": "4", "D": "6"}, "correct_answer": "B"},
    {"id": 20, "difficulty": "easy", "question": "l=20 cm, b=15 cm, lateral surface area = 420 cm². Find h.", "options": {"A": "5 cm", "B": "6 cm", "C": "7 cm", "D": "8 cm"}, "correct_answer": "B"},
    {"id": 21, "difficulty": "medium", "question": "Three cubes of edge 4 cm each are joined end to end. Find surface area of resulting cuboid.", "options": {"A": "224 cm²", "B": "240 cm²", "C": "256 cm²", "D": "272 cm²"}, "correct_answer": "A"},
    {"id": 22, "difficulty": "medium", "question": "The dimensions of cuboid are in ratio 4:3:2. If surface area is 208 cm², find its dimensions.", "options": {"A": "8,6,4 cm", "B": "12,9,6 cm", "C": "16,12,8 cm", "D": "20,15,10 cm"}, "correct_answer": "A"},
    {"id": 23, "difficulty": "medium", "question": "A cuboid has volume 240 cm³. If l=8 cm, b=6 cm, find surface area.", "options": {"A": "236 cm²", "B": "246 cm²", "C": "256 cm²", "D": "266 cm²"}, "correct_answer": "A"},
    {"id": 24, "difficulty": "medium", "question": "If each dimension of cuboid is doubled, surface area becomes how many times?", "options": {"A": "2 times", "B": "3 times", "C": "4 times", "D": "8 times"}, "correct_answer": "C"},
    {"id": 25, "difficulty": "medium", "question": "The lateral surface area of cuboid is 180 cm². If l=10 cm, b=5 cm, find total surface area.", "options": {"A": "280 cm²", "B": "290 cm²", "C": "300 cm²", "D": "310 cm²"}, "correct_answer": "B"},
    {"id": 26, "difficulty": "medium", "question": "A cuboidal box without lid has dimensions 12×10×8 cm. Find surface area.", "options": {"A": "496 cm²", "B": "536 cm²", "C": "576 cm²", "D": "616 cm²"}, "correct_answer": "B"},
    {"id": 27, "difficulty": "medium", "question": "The cost of painting cuboidal hall at ₹5 per m² is ₹1240. If l=12 m, b=8 m, find height.", "options": {"A": "4 m", "B": "5 m", "C": "6 m", "D": "7 m"}, "correct_answer": "B"},
    {"id": 28, "difficulty": "medium", "question": "Two cuboids have dimensions 2×3×4 and 4×6×8. What is ratio of surface areas?", "options": {"A": "1:2", "B": "1:4", "C": "1:6", "D": "1:8"}, "correct_answer": "B"},
    {"id": 29, "difficulty": "medium", "question": "A cuboid has surface area 94 cm². If l=5 cm, b=3 cm, find its volume.", "options": {"A": "30 cm³", "B": "40 cm³", "C": "50 cm³", "D": "60 cm³"}, "correct_answer": "A"},
    {"id": 30, "difficulty": "medium", "question": "The diagonal of cuboid is √77 cm. If l=6 cm, b=3 cm, find surface area.", "options": {"A": "94 cm²", "B": "104 cm²", "C": "114 cm²", "D": "124 cm²"}, "correct_answer": "A"},
    {"id": 31, "difficulty": "medium", "question": "If length increases by 20%, breadth decreases by 10%, height increases by 30%, what is % change in surface area?", "options": {"A": "increase by 40.4%", "B": "increase by 44.4%", "C": "increase by 48.4%", "D": "increase by 52.4%"}, "correct_answer": "A"},
    {"id": 32, "difficulty": "medium", "question": "A cuboid has dimensions such that l=2b=3h. If surface area is 352 cm², find volume.", "options": {"A": "384 cm³", "B": "432 cm³", "C": "480 cm³", "D": "528 cm³"}, "correct_answer": "A"},
    {"id": 33, "difficulty": "medium", "question": "Four cubes of edge 3 cm are joined to form cuboid. Find surface area.", "options": {"A": "162 cm²", "B": "180 cm²", "C": "198 cm²", "D": "216 cm²"}, "correct_answer": "B"},
    {"id": 34, "difficulty": "medium", "question": "The surface area of cuboid is 2.5 times its lateral surface area. If l=10 cm, b=8 cm, find h.", "options": {"A": "4 cm", "B": "5 cm", "C": "6 cm", "D": "7 cm"}, "correct_answer": "C"},
    {"id": 35, "difficulty": "medium", "question": "A cuboidal tank open at top has dimensions 5×4×3 m. Find cost of painting inside at ₹10/m².", "options": {"A": "₹540", "B": "₹640", "C": "₹740", "D": "₹840"}, "correct_answer": "C"},
    {"id": 36, "difficulty": "medium", "question": "If cuboid is made from sheet metal of area 188 cm², with l=8 cm, b=5 cm, find thickness (height).", "options": {"A": "2 cm", "B": "2.5 cm", "C": "3 cm", "D": "3.5 cm"}, "correct_answer": "C"},
    {"id": 37, "difficulty": "medium", "question": "The volume of cuboid is 480 cm³. Surface area is 376 cm². If l=12 cm, find b and h.", "options": {"A": "8,5 cm", "B": "10,4 cm", "C": "6,8 cm", "D": "5,8 cm"}, "correct_answer": "B"},
    {"id": 38, "difficulty": "medium", "question": "A cuboid has all edges integers. If surface area is 94, find possible dimensions.", "options": {"A": "5,4,3", "B": "6,4,2", "C": "7,3,2", "D": "8,2,1"}, "correct_answer": "A"},
    {"id": 39, "difficulty": "medium", "question": "l:b:h = 5:4:3. If surface area = 846 cm², find volume.", "options": {"A": "1260 cm³", "B": "1440 cm³", "C": "1620 cm³", "D": "1800 cm³"}, "correct_answer": "C"},
    {"id": 40, "difficulty": "medium", "question": "A cuboid has same volume as cube of edge 6 cm. If l=9 cm, b=4 cm, find surface area.", "options": {"A": "228 cm²", "B": "248 cm²", "C": "268 cm²", "D": "288 cm²"}, "correct_answer": "D"},
    {"id": 41, "difficulty": "hard", "question": "A cuboid has dimensions 15×12×10 cm. Equal squares cut from corners, remaining folded to form open box. Find surface area of box if square side = 2 cm.", "options": {"A": "476 cm²", "B": "496 cm²", "C": "516 cm²", "D": "536 cm²"}, "correct_answer": "B"},
    {"id": 42, "difficulty": "hard", "question": "The surface area of cuboid is 432 cm². If dimensions are in ratio 3:2:1, find longest diagonal.", "options": {"A": "6√14 cm", "B": "7√14 cm", "C": "8√14 cm", "D": "9√14 cm"}, "correct_answer": "A"},
    {"id": 43, "difficulty": "hard", "question": "A cuboid is cut into two cubes of equal volume. If original surface area was 280 cm², find surface area of each cube.", "options": {"A": "96 cm²", "B": "120 cm²", "C": "144 cm²", "D": "150 cm²"}, "correct_answer": "C"},
    {"id": 44, "difficulty": "hard", "question": "Three cuboids of dimensions 4×3×2, 6×4×3, 8×5×4 are melted to form single cube. Find surface area of cube.", "options": {"A": "384 cm²", "B": "486 cm²", "C": "576 cm²", "D": "600 cm²"}, "correct_answer": "C"},
    {"id": 45, "difficulty": "hard", "question": "The external dimensions of closed wooden box are 12×10×8 cm. Thickness is 1 cm. Find surface area of wood.", "options": {"A": "376 cm²", "B": "396 cm²", "C": "416 cm²", "D": "436 cm²"}, "correct_answer": "C"},
    {"id": 46, "difficulty": "hard", "question": "A cuboid has volume 720 cm³. Surface area is 484 cm². If two dimensions are equal, find dimensions.", "options": {"A": "12,10,6 cm", "B": "15,8,6 cm", "C": "18,5,8 cm", "D": "20,6,6 cm"}, "correct_answer": "A"},
    {"id": 47, "difficulty": "hard", "question": "From cuboid 10×8×6 cm, largest possible cylinder is cut out. Find surface area of remaining solid.", "options": {"A": "480 - 96π cm²", "B": "480 - 112π cm²", "C": "480 - 128π cm²", "D": "480 - 144π cm²"}, "correct_answer": "A"},
    {"id": 48, "difficulty": "hard", "question": "The surface area of cuboid is 2(lb + bh + hl). If l+b+h=19, lb+bh+hl=120, find volume.", "options": {"A": "125", "B": "150", "C": "175", "D": "200"}, "correct_answer": "C"},
    {"id": 49, "difficulty": "hard", "question": "A cuboid has faces with areas 24, 32, 48 cm². Find volume.", "options": {"A": "192 cm³", "B": "216 cm³", "C": "240 cm³", "D": "264 cm³"}, "correct_answer": "A"},
    {"id": 50, "difficulty": "hard", "question": "The cost of painting cuboid inside and outside at ₹8/m² is ₹960. If l=6 m, b=4 m, h=3 m, find thickness if hollow.", "options": {"A": "0.2 m", "B": "0.3 m", "C": "0.4 m", "D": "0.5 m"}, "correct_answer": "D"},
    {"id": 51, "difficulty": "medium", "question": "l=14 cm, b=10 cm, surface area = 652 cm². Find h.", "options": {"A": "6 cm", "B": "7 cm", "C": "8 cm", "D": "9 cm"}, "correct_answer": "C"},
    {"id": 52, "difficulty": "medium", "question": "If all dimensions increase by 10%, surface area increases by?", "options": {"A": "20%", "B": "21%", "C": "22%", "D": "23%"}, "correct_answer": "B"},
    {"id": 53, "difficulty": "medium", "question": "Cuboid volume 600 cm³. l=15 cm, b=8 cm. Surface area?", "options": {"A": "460 cm²", "B": "480 cm²", "C": "500 cm²", "D": "520 cm²"}, "correct_answer": "A"},
    {"id": 54, "difficulty": "medium", "question": "l:b:h = 2:1:1. Surface area = 160 cm². Find volume.", "options": {"A": "128 cm³", "B": "144 cm³", "C": "160 cm³", "D": "176 cm³"}, "correct_answer": "A"},
    {"id": 55, "difficulty": "medium", "question": "Cuboid open at top: l=12, b=9, h=6. Surface area?", "options": {"A": "396 cm²", "B": "414 cm²", "C": "432 cm²", "D": "450 cm²"}, "correct_answer": "B"},
    {"id": 56, "difficulty": "medium", "question": "Surface area 376 m², l=10 m, b=8 m. Height?", "options": {"A": "5 m", "B": "6 m", "C": "7 m", "D": "8 m"}, "correct_answer": "B"},
    {"id": 57, "difficulty": "medium", "question": "Two cubes edge 5 cm joined. Surface area of cuboid?", "options": {"A": "250 cm²", "B": "275 cm²", "C": "300 cm²", "D": "325 cm²"}, "correct_answer": "A"},
    {"id": 58, "difficulty": "medium", "question": "l increases by 20%, b by 30%, h decreases by 10%. Net surface area change?", "options": {"A": "+40.4%", "B": "+42.4%", "C": "+44.4%", "D": "+46.4%"}, "correct_answer": "B"},
    {"id": 59, "difficulty": "medium", "question": "Cuboid diagonal √149 cm. l=10, b=5. Surface area?", "options": {"A": "230 cm²", "B": "240 cm²", "C": "250 cm²", "D": "260 cm²"}, "correct_answer": "A"},
    {"id": 60, "difficulty": "medium", "question": "Cost of painting ₹5/m² is ₹470. l=9 m, b=5 m. Find h.", "options": {"A": "3 m", "B": "4 m", "C": "5 m", "D": "6 m"}, "correct_answer": "B"},
    {"id": 61, "difficulty": "medium", "question": "Volume 480 cm³. l=12, b=8. Surface area?", "options": {"A": "352 cm²", "B": "372 cm²", "C": "392 cm²", "D": "412 cm²"}, "correct_answer": "C"},
    {"id": 62, "difficulty": "medium", "question": "l=2b=4h. Surface area = 2800 cm². Volume?", "options": {"A": "8000 cm³", "B": "10000 cm³", "C": "12000 cm³", "D": "14000 cm³"}, "correct_answer": "A"},
    {"id": 63, "difficulty": "medium", "question": "Three cubes edge 4 cm joined. Surface area?", "options": {"A": "224 cm²", "B": "240 cm²", "C": "256 cm²", "D": "272 cm²"}, "correct_answer": "A"},
    {"id": 64, "difficulty": "medium", "question": "Cuboid open: l=15, b=10, h=8. Metal used?", "options": {"A": "550 cm²", "B": "600 cm²", "C": "650 cm²", "D": "700 cm²"}, "correct_answer": "A"},
    {"id": 65, "difficulty": "medium", "question": "Surface area 94, l=5, b=4. Volume?", "options": {"A": "30", "B": "40", "C": "50", "D": "60"}, "correct_answer": "A"},
    {"id": 66, "difficulty": "medium", "question": "l:b:h = 3:2:1. Surface area 352. Dimensions?", "options": {"A": "12,8,4", "B": "15,10,5", "C": "18,12,6", "D": "21,14,7"}, "correct_answer": "A"},
    {"id": 67, "difficulty": "medium", "question": "Four cubes edge 3 joined. Surface area?", "options": {"A": "180 cm²", "B": "198 cm²", "C": "216 cm²", "D": "234 cm²"}, "correct_answer": "B"},
    {"id": 68, "difficulty": "medium", "question": "Diagonal √77, l=6, b=3. Surface area?", "options": {"A": "94", "B": "104", "C": "114", "D": "124"}, "correct_answer": "A"},
    {"id": 69, "difficulty": "medium", "question": "l=10, b=8, lateral surface = 216. Total surface?", "options": {"A": "376", "B": "396", "C": "416", "D": "436"}, "correct_answer": "C"},
    {"id": 70, "difficulty": "medium", "question": "Volume 240, l=8, b=6. Surface area?", "options": {"A": "236", "B": "246", "C": "256", "D": "266"}, "correct_answer": "A"},
    {"id": 71, "difficulty": "hard", "question": "Cuboid cut into 8 cubes of edge 3 cm. Original surface area?", "options": {"A": "396 cm²", "B": "432 cm²", "C": "468 cm²", "D": "504 cm²"}, "correct_answer": "B"},
    {"id": 72, "difficulty": "hard", "question": "External: 12×10×8, thickness 1. Wood surface area?", "options": {"A": "416", "B": "436", "C": "456", "D": "476"}, "correct_answer": "A"},
    {"id": 73, "difficulty": "hard", "question": "Surface area 432, ratio 3:2:1. Volume?", "options": {"A": "192", "B": "216", "C": "240", "D": "264"}, "correct_answer": "A"},
    {"id": 74, "difficulty": "hard", "question": "l+b+h=19, lb+bh+hl=120. Volume?", "options": {"A": "125", "B": "150", "C": "175", "D": "200"}, "correct_answer": "C"},
    {"id": 75, "difficulty": "hard", "question": "Faces areas 24, 32, 48. Volume?", "options": {"A": "192", "B": "216", "C": "240", "D": "264"}, "correct_answer": "A"},
    {"id": 76, "difficulty": "hard", "question": "From 10×8×6, cylinder radius 4 cut. Remaining surface?", "options": {"A": "480-96π", "B": "480-112π", "C": "480-128π", "D": "480-144π"}, "correct_answer": "A"},
    {"id": 77, "difficulty": "hard", "question": "Three cuboids: 4×3×2, 6×4×3, 8×5×4 melted to cube. Cube surface area?", "options": {"A": "384", "B": "486", "C": "576", "D": "600"}, "correct_answer": "C"},
    {"id": 78, "difficulty": "hard", "question": "Cuboid to two equal cubes. Original SA 280. Each cube SA?", "options": {"A": "96", "B": "120", "C": "144", "D": "150"}, "correct_answer": "C"},
    {"id": 79, "difficulty": "hard", "question": "15×12×10, squares 2 cm cut from corners. Box surface area?", "options": {"A": "496", "B": "516", "C": "536", "D": "556"}, "correct_answer": "A"},
    {"id": 80, "difficulty": "hard", "question": "Paint inside & outside ₹8/m² = ₹960. l=6, b=4, h=3. Thickness?", "options": {"A": "0.3", "B": "0.4", "C": "0.5", "D": "0.6"}, "correct_answer": "C"},
    {"id": 81, "difficulty": "easy", "question": "l=7, b=5, h=3. Surface area?", "options": {"A": "142", "B": "152", "C": "162", "D": "172"}, "correct_answer": "A"},
    {"id": 82, "difficulty": "easy", "question": "Cube edge 5 cm is what type of cuboid?", "options": {"A": "l=b=h", "B": "l≠b=h", "C": "l=b≠h", "D": "all different"}, "correct_answer": "A"},
    {"id": 83, "difficulty": "easy", "question": "l=9, b=6, h=4. Lateral surface?", "options": {"A": "100", "B": "110", "C": "120", "D": "130"}, "correct_answer": "C"},
    {"id": 84, "difficulty": "easy", "question": "Surface area formula?", "options": {"A": "2(l+b)h", "B": "2(lb+bh+hl)", "C": "lbh", "D": "l+b+h"}, "correct_answer": "B"},
    {"id": 85, "difficulty": "easy", "question": "How many faces cuboid?", "options": {"A": "4", "B": "5", "C": "6", "D": "8"}, "correct_answer": "C"},
    {"id": 86, "difficulty": "medium", "question": "l=12, b=8, SA=432. Height?", "options": {"A": "5", "B": "6", "C": "7", "D": "8"}, "correct_answer": "B"},
    {"id": 87, "difficulty": "medium", "question": "All dimensions double. SA becomes?", "options": {"A": "2 times", "B": "3 times", "C": "4 times", "D": "8 times"}, "correct_answer": "C"},
    {"id": 88, "difficulty": "medium", "question": "Volume 360, l=12, b=6. Surface area?", "options": {"A": "324", "B": "336", "C": "348", "D": "360"}, "correct_answer": "A"},
    {"id": 89, "difficulty": "medium", "question": "Two cubes edge 6 joined. SA of cuboid?", "options": {"A": "360", "B": "380", "C": "400", "D": "420"}, "correct_answer": "A"},
    {"id": 90, "difficulty": "hard", "question": "l=2b=3h, SA=352. Volume?", "options": {"A": "384", "B": "432", "C": "480", "D": "528"}, "correct_answer": "A"},
    {"id": 91, "difficulty": "hard", "question": "Faces areas 30, 42, 35. Volume?", "options": {"A": "210", "B": "220", "C": "230", "D": "240"}, "correct_answer": "A"},
    {"id": 92, "difficulty": "easy", "question": "l=11, b=7, h=5. Surface area?", "options": {"A": "334", "B": "344", "C": "354", "D": "364"}, "correct_answer": "A"},
    {"id": 93, "difficulty": "easy", "question": "Cube edge 8. Surface area?", "options": {"A": "384", "B": "394", "C": "404", "D": "414"}, "correct_answer": "A"},
    {"id": 94, "difficulty": "medium", "question": "l:b:h = 4:3:2. SA=208. Dimensions?", "options": {"A": "8,6,4", "B": "12,9,6", "C": "16,12,8", "D": "20,15,10"}, "correct_answer": "A"},
    {"id": 95, "difficulty": "medium", "question": "Open box: l=10, b=8, h=6. Metal area?", "options": {"A": "328", "B": "348", "C": "368", "D": "388"}, "correct_answer": "A"},
    {"id": 96, "difficulty": "hard", "question": "SA=484, volume=720, two dimensions equal. Dimensions?", "options": {"A": "12,10,6", "B": "15,8,6", "C": "18,5,8", "D": "20,6,6"}, "correct_answer": "A"},
    {"id": 97, "difficulty": "hard", "question": "l+b+h=15, lb+bh+hl=71. Volume?", "options": {"A": "105", "B": "120", "C": "135", "D": "150"}, "correct_answer": "A"},
    {"id": 98, "difficulty": "easy", "question": "l=2.5, b=2, h=1.5. Surface area?", "options": {"A": "23.5", "B": "24.5", "C": "25.5", "D": "26.5"}, "correct_answer": "A"},
    {"id": 99, "difficulty": "easy", "question": "Lateral surface formula?", "options": {"A": "2h(l+b)", "B": "2(lb+bh)", "C": "lb+bh+hl", "D": "2(l+b+h)"}, "correct_answer": "A"},
    {"id": 100, "difficulty": "medium", "question": "Volume 512, l=16, b=8. Surface area?", "options": {"A": "352", "B": "372", "C": "392", "D": "412"}, "correct_answer": "A"}
  ]
}