Average


  1. Six tables and twelve chairs were bought for ₹ 7,800. If the average price of a table is ₹ 750, then the average price of a chair would be









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    Here , Six tables and twelve chairs bought = ₹ 7,800
    The average price of a table = ₹ 750
    Average cost of a chair = ₹ y , then
    y × 12 + 6 × 750 = 7800
    ⇒ 12y = 7800 – 4500 = 3300

    Correct Option: B

    Here , Six tables and twelve chairs bought = ₹ 7,800
    The average price of a table = ₹ 750
    Average cost of a chair = ₹ y , then
    y × 12 + 6 × 750 = 7800
    ⇒ 12y = 7800 – 4500 = 3300

    ⇒ y =
    3300
    = 275
    12


  1. 4 boys and 3 girls spent ₹ 120 on the average, of which boys spent ₹ 150 on the average. Then the average amount spent by the girls is









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    The average of 4 boys and 3 girls on expenditure = ₹ 120
    Total expenditure = 120 × 7 = Rs. 840
    The average of 4 boys on expenditure = ₹ 150
    Total expenditure of 4 boys = 150 × 4 = 600
    Total expenditure of 3 girls = Total expenditure - Total expenditure of 4 boys
    Total expenditure of 3 girls = 840 – 600 = 240

    Correct Option: A

    The average of 4 boys and 3 girls on expenditure = ₹ 120
    Total expenditure = 120 × 7 = Rs. 840
    The average of 4 boys on expenditure = ₹ 150
    Total expenditure of 4 boys = 150 × 4 = 600
    Total expenditure of 3 girls = Total expenditure - Total expenditure of 4 boys
    Total expenditure of 3 girls = 840 – 600 = 240

    ∴ Their average expenditure =
    240
    = 80
    3



  1. The average weight of five persons sitting in a boat is 38 kg. The average weight of the boat and the persons sitting in the boat is 52 kg. What is the weight of the boat ?









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    Given that , The average weight of five persons sitting in a boat = 38 kg.
    Sum of weight of five persons = 5 × 38 = 190
    The average weight of the boat and the persons sitting in the boat = 52 kg.
    Sum of weight of the boat and five persons = 6 × 52 = 312

    Correct Option: B

    Given that , The average weight of five persons sitting in a boat = 38 kg.
    Sum of weight of five persons = 5 × 38 = 190
    The average weight of the boat and the persons sitting in the boat = 52 kg.
    Sum of weight of the boat and five persons = 6 × 52 = 312
    ∴ Weight of the boat = Sum of weight of the boat and five persons – Sum of weight of five persons
    Weight of the boat = 312 – 190 = 122 kg


  1. The average of 10 numbers is 7. If each number is multiplied by 12, then the average of the new set of numbers will be









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    As we know that If each number is multiplied by a certain number, then the average is also multiplied by that number.
    Given , The average of 10 numbers = 7

    Correct Option: D

    As we know that If each number is multiplied by a certain number, then the average is also multiplied by that number.
    Given , The average of 10 numbers = 7
    ∴ Required average = 7 × 12 = 84



  1. A student was asked to find the arithmetic mean of the following 12 numbers :
    3, 11, 7, 9, 15, 13, 8, 19, 17, 21, 14 and y
    He found the mean to be 12. The value of y will be :









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    As we know that ,

    Average or Mean =
    Sum of quantities
    Total number of quantities

    Mean =
    3 + 11 + 9 + 7 + 15 + 13 + 8 + 19 + 17 + 21 + 14 + y
    12

    According to question,

    Correct Option: B

    As we know that ,

    Average or Mean =
    Sum of quantities
    Total number of quantities

    Mean =
    3 + 11 + 9 + 7 + 15 + 13 + 8 + 19 + 17 + 21 + 14 + y
    12

    According to question,
    12 =
    137 + y
    12

    ∴ 137 + y = 144
    ∴ y = 144 - 137 = 7