{
  "title": "Mean - Grade 9 CBSE",
  "total_questions": 100,
  "questions": [
    {"id": 1, "difficulty": "easy", "question": "Mean is also called:", "options": {"A": "Average", "B": "Middle value", "C": "Most frequent", "D": "Range"}, "correct_answer": "A"},
    {"id": 2, "difficulty": "easy", "question": "Formula for mean of n values: sum of values divided by:", "options": {"A": "n", "B": "n+1", "C": "n-1", "D": "2n"}, "correct_answer": "A"},
    {"id": 3, "difficulty": "easy", "question": "For data: 4,6,8,10, mean is:", "options": {"A": "6", "B": "7", "C": "8", "D": "9"}, "correct_answer": "B"},
    {"id": 4, "difficulty": "easy", "question": "Mean is a measure of:", "options": {"A": "Central tendency", "B": "Dispersion", "C": "Correlation", "D": "Probability"}, "correct_answer": "A"},
    {"id": 5, "difficulty": "easy", "question": "If all values are equal, mean equals:", "options": {"A": "That value", "B": "Zero", "C": "One", "D": "Sum"}, "correct_answer": "A"},
    {"id": 6, "difficulty": "easy", "question": "For data: 5,10,15,20,25, mean:", "options": {"A": "10", "B": "12.5", "C": "15", "D": "17.5"}, "correct_answer": "C"},
    {"id": 7, "difficulty": "easy", "question": "Mean is affected by:", "options": {"A": "Extreme values", "B": "Middle values only", "C": "First value only", "D": "Last value only"}, "correct_answer": "A"},
    {"id": 8, "difficulty": "easy", "question": "If each value increases by 5, mean increases by:", "options": {"A": "0", "B": "5", "C": "10", "D": "n×5"}, "correct_answer": "B"},
    {"id": 9, "difficulty": "easy", "question": "If each value is multiplied by 3, mean is multiplied by:", "options": {"A": "1", "B": "3", "C": "9", "D": "27"}, "correct_answer": "B"},
    {"id": 10, "difficulty": "easy", "question": "For data: 12,15,18, mean:", "options": {"A": "12", "B": "15", "C": "18", "D": "45"}, "correct_answer": "B"},
    {"id": 11, "difficulty": "easy", "question": "Sum of deviations from mean is:", "options": {"A": "0", "B": "1", "C": "n", "D": "Mean"}, "correct_answer": "A"},
    {"id": 12, "difficulty": "easy", "question": "For grouped data, mean uses:", "options": {"A": "Class marks", "B": "Class limits", "C": "Frequencies", "D": "Both A and C"}, "correct_answer": "D"},
    {"id": 13, "difficulty": "easy", "question": "If mean of 5 numbers is 20, their sum is:", "options": {"A": "4", "B": "20", "C": "100", "D": "120"}, "correct_answer": "C"},
    {"id": 14, "difficulty": "easy", "question": "Data: 8,9,10,11,12. Mean?", "options": {"A": "9", "B": "10", "C": "11", "D": "12"}, "correct_answer": "B"},
    {"id": 15, "difficulty": "easy", "question": "If a value is added to data, mean:", "options": {"A": "Always increases", "B": "Always decreases", "C": "May change", "D": "Stays same"}, "correct_answer": "C"},
    {"id": 16, "difficulty": "easy", "question": "For data: 2,4,6,8,10,12, mean:", "options": {"A": "6", "B": "7", "C": "8", "D": "9"}, "correct_answer": "B"},
    {"id": 17, "difficulty": "easy", "question": "Mean of first 5 natural numbers:", "options": {"A": "2", "B": "3", "C": "4", "D": "5"}, "correct_answer": "B"},
    {"id": 18, "difficulty": "easy", "question": "If mean=15 and sum=75, number of values:", "options": {"A": "3", "B": "4", "C": "5", "D": "6"}, "correct_answer": "C"},
    {"id": 19, "difficulty": "easy", "question": "Data: 20,25,30,35,40. Mean?", "options": {"A": "25", "B": "30", "C": "35", "D": "40"}, "correct_answer": "B"},
    {"id": 20, "difficulty": "easy", "question": "Arithmetic mean is another name for:", "options": {"A": "Median", "B": "Mode", "C": "Mean", "D": "Range"}, "correct_answer": "C"},
    
    {"id": 21, "difficulty": "medium", "question": "Find mean: 12,15,18,21,24", "options": {"A": "15", "B": "16", "C": "17", "D": "18"}, "correct_answer": "D"},
    {"id": 22, "difficulty": "medium", "question": "Data: 25,30,35,40,45,50. Mean?", "options": {"A": "35", "B": "36", "C": "37.5", "D": "40"}, "correct_answer": "C"},
    {"id": 23, "difficulty": "medium", "question": "Find mean: 8,12,6,15,10,18,14", "options": {"A": "10", "B": "11", "C": "12", "D": "13"}, "correct_answer": "C"},
    {"id": 24, "difficulty": "medium", "question": "Data: 42,38,45,36,40,48,32. Mean?", "options": {"A": "38", "B": "40", "C": "41.5", "D": "42"}, "correct_answer": "C"},
    {"id": 25, "difficulty": "medium", "question": "Find mean: 5.5,6.0,4.5,7.0,5.0,6.5,5.8", "options": {"A": "5.5", "B": "5.76", "C": "5.9", "D": "6.0"}, "correct_answer": "B"},
    {"id": 26, "difficulty": "medium", "question": "Data: 120,150,130,140,160,110,170. Mean?", "options": {"A": "130", "B": "137.14", "C": "140", "D": "150"}, "correct_answer": "B"},
    {"id": 27, "difficulty": "medium", "question": "Find mean: 22,18,25,30,15,28,20,35", "options": {"A": "22", "B": "23.875", "C": "24", "D": "25"}, "correct_answer": "B"},
    {"id": 28, "difficulty": "medium", "question": "Data: 7,12,8,15,10,18,13,20. Mean?", "options": {"A": "11.5", "B": "12", "C": "12.875", "D": "13"}, "correct_answer": "C"},
    {"id": 29, "difficulty": "medium", "question": "Find mean: 45,55,35,65,40,60,50,70", "options": {"A": "47.5", "B": "50", "C": "52.5", "D": "55"}, "correct_answer": "C"},
    {"id": 30, "difficulty": "medium", "question": "Data: 3.2,4.5,2.8,5.1,3.9,4.2,3.5. Mean?", "options": {"A": "3.5", "B": "3.86", "C": "4.0", "D": "4.2"}, "correct_answer": "B"},
    {"id": 31, "difficulty": "medium", "question": "Find mean: 100,120,80,140,110,130,90,150", "options": {"A": "110", "B": "115", "C": "120", "D": "125"}, "correct_answer": "B"},
    {"id": 32, "difficulty": "medium", "question": "Data: 14,18,12,22,16,20,24,10. Mean?", "options": {"A": "16", "B": "17", "C": "18", "D": "19"}, "correct_answer": "B"},
    {"id": 33, "difficulty": "medium", "question": "Find mean: 6,12,8,15,10,18,13,20,9", "options": {"A": "10", "B": "11", "C": "12", "D": "13"}, "correct_answer": "C"},
    {"id": 34, "difficulty": "medium", "question": "Data: 25,35,20,40,30,45,15,50,10. Mean?", "options": {"A": "25", "B": "28.33", "C": "30", "D": "35"}, "correct_answer": "B"},
    {"id": 35, "difficulty": "medium", "question": "Find mean: 2.5,3.0,1.8,4.2,2.0,3.5,2.8,4.0", "options": {"A": "2.5", "B": "2.85", "C": "3.0", "D": "3.2"}, "correct_answer": "B"},
    {"id": 36, "difficulty": "medium", "question": "Data: 55,65,45,75,60,70,50,80,40. Mean?", "options": {"A": "55", "B": "58.33", "C": "60", "D": "65"}, "correct_answer": "B"},
    {"id": 37, "difficulty": "medium", "question": "Find mean: 12,18,15,24,20,30,22,28,16", "options": {"A": "18", "B": "19.44", "C": "20", "D": "21"}, "correct_answer": "B"},
    {"id": 38, "difficulty": "medium", "question": "Data: 7.5,8.2,6.8,9.0,7.0,8.5,6.5,9.5. Mean?", "options": {"A": "7.5", "B": "7.88", "C": "8.0", "D": "8.25"}, "correct_answer": "B"},
    {"id": 39, "difficulty": "medium", "question": "Find mean: 150,180,120,200,160,190,140,210,130", "options": {"A": "150", "B": "158.89", "C": "160", "D": "170"}, "correct_answer": "B"},
    {"id": 40, "difficulty": "medium", "question": "Data: 11,22,15,28,19,33,24,30,17. Mean?", "options": {"A": "19", "B": "21", "C": "22", "D": "24"}, "correct_answer": "B"},
    {"id": 41, "difficulty": "medium", "question": "Find mean: 4.8,5.2,3.9,6.1,4.5,5.8,4.0,6.0", "options": {"A": "4.8", "B": "5.03", "C": "5.2", "D": "5.4"}, "correct_answer": "B"},
    {"id": 42, "difficulty": "medium", "question": "Data: 85,95,75,105,90,100,80,110,70. Mean?", "options": {"A": "85", "B": "88.89", "C": "90", "D": "95"}, "correct_answer": "B"},
    {"id": 43, "difficulty": "medium", "question": "Find mean: 16,24,18,30,22,36,26,32,20", "options": {"A": "22", "B": "24", "C": "25.11", "D": "26"}, "correct_answer": "C"},
    {"id": 44, "difficulty": "medium", "question": "Data: 3.5,4.8,2.9,5.2,3.0,4.5,2.5,5.0. Mean?", "options": {"A": "3.5", "B": "3.93", "C": "4.0", "D": "4.5"}, "correct_answer": "B"},
    {"id": 45, "difficulty": "medium", "question": "Find mean: 200,250,150,300,220,280,180,320,170", "options": {"A": "200", "B": "216.67", "C": "230", "D": "250"}, "correct_answer": "B"},
    {"id": 46, "difficulty": "medium", "question": "Data: 9,18,12,24,15,30,21,27,6. Mean?", "options": {"A": "15", "B": "16.67", "C": "18", "D": "20"}, "correct_answer": "B"},
    {"id": 47, "difficulty": "medium", "question": "Find mean: 6.5,7.8,5.2,8.4,6.0,7.5,5.5,8.0", "options": {"A": "6.5", "B": "6.86", "C": "7.0", "D": "7.25"}, "correct_answer": "B"},
    {"id": 48, "difficulty": "medium", "question": "Data: 44,55,33,66,40,60,36,70,50. Mean?", "options": {"A": "44", "B": "48.44", "C": "50", "D": "55"}, "correct_answer": "B"},
    {"id": 49, "difficulty": "medium", "question": "Find mean: 18,27,21,36,24,42,30,39,15", "options": {"A": "24", "B": "26", "C": "28", "D": "30"}, "correct_answer": "C"},
    {"id": 50, "difficulty": "medium", "question": "Data: 8.5,9.2,7.8,10.1,8.0,9.5,7.5,10.0. Mean?", "options": {"A": "8.5", "B": "8.83", "C": "9.0", "D": "9.25"}, "correct_answer": "B"},
    {"id": 51, "difficulty": "medium", "question": "Find mean: 120,150,100,180,130,170,110,190,140", "options": {"A": "130", "B": "138.89", "C": "140", "D": "150"}, "correct_answer": "B"},
    {"id": 52, "difficulty": "medium", "question": "Data: 13,26,17,32,21,28,24,30,19. Mean?", "options": {"A": "21", "B": "23", "C": "24", "D": "26"}, "correct_answer": "B"},
    {"id": 53, "difficulty": "medium", "question": "Find mean: 5.2,6.5,4.3,7.2,5.0,6.8,4.5,7.0", "options": {"A": "5.2", "B": "5.81", "C": "6.0", "D": "6.4"}, "correct_answer": "B"},
    {"id": 54, "difficulty": "medium", "question": "Data: 77,88,66,99,70,95,73,100,80. Mean?", "options": {"A": "80", "B": "83.11", "C": "85", "D": "88"}, "correct_answer": "B"},
    {"id": 55, "difficulty": "medium", "question": "Find mean: 25,38,29,45,32,50,36,48,30", "options": {"A": "32", "B": "34.78", "C": "36", "D": "38"}, "correct_answer": "B"},
    {"id": 56, "difficulty": "medium", "question": "Data: 9.5,10.8,8.2,11.5,9.0,11.0,8.5,11.2. Mean?", "options": {"A": "9.5", "B": "9.96", "C": "10.0", "D": "10.5"}, "correct_answer": "B"},
    {"id": 57, "difficulty": "medium", "question": "Find mean: 160,200,140,240,180,220,150,260,170", "options": {"A": "180", "B": "188.89", "C": "190", "D": "200"}, "correct_answer": "B"},
    {"id": 58, "difficulty": "medium", "question": "Data: 14,28,18,35,22,30,25,32,20. Mean?", "options": {"A": "22", "B": "24", "C": "25.78", "D": "28"}, "correct_answer": "B"},
    {"id": 59, "difficulty": "medium", "question": "Find mean: 6.8,8.2,5.5,9.0,6.2,8.5,5.8,9.2", "options": {"A": "6.8", "B": "7.39", "C": "7.5", "D": "8.2"}, "correct_answer": "B"},
    {"id": 60, "difficulty": "medium", "question": "Data: 99,110,88,120,95,115,92,125,100. Mean?", "options": {"A": "100", "B": "104.89", "C": "110", "D": "115"}, "correct_answer": "B"},
    {"id": 61, "difficulty": "medium", "question": "Find mean: 32,48,38,56,42,60,46,58,40", "options": {"A": "42", "B": "44.67", "C": "46", "D": "48"}, "correct_answer": "B"},
    {"id": 62, "difficulty": "medium", "question": "Data: 10.5,12.8,9.2,13.5,10.0,12.5,9.5,13.0. Mean?", "options": {"A": "10.5", "B": "11.38", "C": "12.0", "D": "12.5"}, "correct_answer": "B"},
    {"id": 63, "difficulty": "medium", "question": "Find mean: 180,220,160,260,200,240,170,280,190", "options": {"A": "200", "B": "211.11", "C": "220", "D": "230"}, "correct_answer": "B"},
    {"id": 64, "difficulty": "medium", "question": "Data: 17,34,22,42,28,38,31,40,25. Mean?", "options": {"A": "28", "B": "30.78", "C": "31", "D": "34"}, "correct_answer": "B"},
    {"id": 65, "difficulty": "medium", "question": "Find mean: 7.8,9.5,6.8,10.2,7.5,9.8,7.0,10.0", "options": {"A": "7.8", "B": "8.46", "C": "8.5", "D": "9.5"}, "correct_answer": "B"},
    {"id": 66, "difficulty": "medium", "question": "Data: 121,143,110,165,132,154,125,176,115. Mean?", "options": {"A": "132", "B": "137.89", "C": "143", "D": "154"}, "correct_answer": "B"},
    {"id": 67, "difficulty": "medium", "question": "Find mean: 45,68,52,75,58,80,62,78,55", "options": {"A": "58", "B": "60.33", "C": "62", "D": "68"}, "correct_answer": "B"},
    {"id": 68, "difficulty": "medium", "question": "Data: 11.8,14.2,10.2,15.0,11.5,14.5,10.8,15.2. Mean?", "options": {"A": "12.15", "B": "12.65", "C": "13.0", "D": "14.2"}, "correct_answer": "B"},
    {"id": 69, "difficulty": "medium", "question": "Find mean: 240,300,210,360,270,330,230,380,250", "options": {"A": "270", "B": "278.89", "C": "300", "D": "330"}, "correct_answer": "B"},
    {"id": 70, "difficulty": "medium", "question": "Data: 19,38,25,46,31,42,35,44,28. Mean?", "options": {"A": "31", "B": "34.22", "C": "35", "D": "38"}, "correct_answer": "B"},
    {"id": 71, "difficulty": "medium", "question": "Find mean: 8.9,10.8,7.8,11.5,8.5,11.0,8.0,11.2", "options": {"A": "8.9", "B": "9.46", "C": "9.5", "D": "10.8"}, "correct_answer": "B"},
    {"id": 72, "difficulty": "medium", "question": "Data: 132,165,120,180,144,172,136,188,128. Mean?", "options": {"A": "144", "B": "150.56", "C": "165", "D": "172"}, "correct_answer": "B"},
    {"id": 73, "difficulty": "medium", "question": "Find mean: 55,82,64,90,70,96,76,94,68", "options": {"A": "70", "B": "74.11", "C": "76", "D": "82"}, "correct_answer": "B"},
    {"id": 74, "difficulty": "medium", "question": "Data: 13.2,16.5,11.8,17.2,12.5,16.8,12.0,17.0. Mean?", "options": {"A": "13.85", "B": "14.38", "C": "14.5", "D": "16.5"}, "correct_answer": "B"},
    {"id": 75, "difficulty": "medium", "question": "Find mean: 300,380,270,420,330,400,290,440,310", "options": {"A": "330", "B": "348.89", "C": "380", "D": "400"}, "correct_answer": "B"},
    {"id": 76, "difficulty": "medium", "question": "Data: 23,46,30,54,37,50,42,52,35. Mean?", "options": {"A": "37", "B": "41", "C": "42", "D": "46"}, "correct_answer": "B"},
    {"id": 77, "difficulty": "medium", "question": "Find mean: 10.2,12.8,9.2,13.5,10.0,12.5,9.5,13.0", "options": {"A": "10.6", "B": "11.34", "C": "12.0", "D": "12.5"}, "correct_answer": "B"},
    {"id": 78, "difficulty": "medium", "question": "Data: 154,192,140,210,168,200,152,220,160. Mean?", "options": {"A": "168", "B": "177.33", "C": "180", "D": "192"}, "correct_answer": "B"},
    {"id": 79, "difficulty": "medium", "question": "Find mean: 68,102,78,115,85,120,92,118,80", "options": {"A": "85", "B": "91.11", "C": "92", "D": "102"}, "correct_answer": "B"},
    {"id": 80, "difficulty": "medium", "question": "Data: 15.8,19.2,14.0,20.5,16.5,19.8,15.0,20.2. Mean?", "options": {"A": "17.15", "B": "17.63", "C": "18.0", "D": "19.2"}, "correct_answer": "B"},
    
    {"id": 81, "difficulty": "hard", "question": "For grouped data with class marks 15,25,35,45 and frequencies 4,8,12,6, mean = ?", "options": {"A": "28", "B": "30", "C": "32", "D": "34"}, "correct_answer": "C"},
    {"id": 82, "difficulty": "hard", "question": "Data: 12,15,18,12,20,15,18,12,15,20,18,12. Find mean.", "options": {"A": "14.5", "B": "15", "C": "15.5", "D": "16"}, "correct_answer": "C"},
    {"id": 83, "difficulty": "hard", "question": "For frequency distribution: Value:10 Freq:3, Value:20 Freq:5, Value:30 Freq:7, Value:40 Freq:4. Mean?", "options": {"A": "25", "B": "27.37", "C": "30", "D": "32.63"}, "correct_answer": "B"},
    {"id": 84, "difficulty": "hard", "question": "If mean of 20 numbers is 35 and each is multiplied by 2, new mean?", "options": {"A": "35", "B": "70", "C": "105", "D": "140"}, "correct_answer": "B"},
    {"id": 85, "difficulty": "hard", "question": "Data: 25,30,35,40,25,30,35,25,40,30,35,25,30. Find mean.", "options": {"A": "30", "B": "30.77", "C": "31", "D": "32"}, "correct_answer": "B"},
    {"id": 86, "difficulty": "hard", "question": "For grouped data: 10-20:5,20-30:12,30-40:18,40-50:10,50-60:5. Mean (approx)?", "options": {"A": "32", "B": "34", "C": "36", "D": "38"}, "correct_answer": "B"},
    {"id": 87, "difficulty": "hard", "question": "If mean of a,b,c is 20, mean of 2a,2b,2c is:", "options": {"A": "20", "B": "40", "C": "60", "D": "80"}, "correct_answer": "B"},
    {"id": 88, "difficulty": "hard", "question": "For data: 5,10,15,20,25 each appearing 4 times, mean?", "options": {"A": "10", "B": "15", "C": "20", "D": "25"}, "correct_answer": "B"},
    {"id": 89, "difficulty": "hard", "question": "Mean of first n natural numbers is:", "options": {"A": "n/2", "B": "(n+1)/2", "C": "n(n+1)/2", "D": "n²/2"}, "correct_answer": "B"},
    {"id": 90, "difficulty": "hard", "question": "Data: 18,22,25,30,18,25,22,30,18,25,22,18. Find mean.", "options": {"A": "21", "B": "22", "C": "23", "D": "24"}, "correct_answer": "C"},
    {"id": 91, "difficulty": "hard", "question": "For grouped data with assumed mean A=35, Σfidi=-100, Σfi=50, mean=?", "options": {"A": "33", "B": "34", "C": "35", "D": "36"}, "correct_answer": "A"},
    {"id": 92, "difficulty": "hard", "question": "If mean of 15 numbers is 40 and two numbers 25,35 are removed, new mean?", "options": {"A": "40", "B": "41.15", "C": "42.31", "D": "43.46"}, "correct_answer": "B"},
    {"id": 93, "difficulty": "hard", "question": "Data has mean=45, median=42, mode=40. Mean is:", "options": {"A": "Less than median", "B": "Equal to median", "C": "Greater than median", "D": "Cannot say"}, "correct_answer": "C"},
    {"id": 94, "difficulty": "hard", "question": "For continuous data, mean is at:", "options": {"A": "Balance point", "B": "Peak", "C": "Left tail", "D": "Right tail"}, "correct_answer": "A"},
    {"id": 95, "difficulty": "hard", "question": "If mean > median > mode, distribution is:", "options": {"A": "Symmetric", "B": "Positively skewed", "C": "Negatively skewed", "D": "Uniform"}, "correct_answer": "B"},
    {"id": 96, "difficulty": "hard", "question": "For symmetric distribution, mean equals:", "options": {"A": "Median", "B": "Mode", "C": "Both A and B", "D": "Neither"}, "correct_answer": "C"},
    {"id": 97, "difficulty": "hard", "question": "Mean for grouped data: Mean = A + (Σfidi/Σfi). A is:", "options": {"A": "Assumed mean", "B": "Actual mean", "C": "Median", "D": "Mode"}, "correct_answer": "A"},
    {"id": 98, "difficulty": "hard", "question": "If all classes have same frequency and same width, mean is:", "options": {"A": "Middle class mark", "B": "First class mark", "C": "Last class mark", "D": "Cannot determine"}, "correct_answer": "A"},
    {"id": 99, "difficulty": "hard", "question": "Weighted mean gives more importance to:", "options": {"A": "Some values", "B": "All values equally", "C": "First value", "D": "Last value"}, "correct_answer": "A"},
    {"id": 100, "difficulty": "hard", "question": "For perfect normal distribution, mean, median, mode:", "options": {"A": "Are equal", "B": "Mean<median<mode", "C": "Mode<median<mean", "D": "All different"}, "correct_answer": "A"}
  ]
}