Average


  1. The average of 10 number is calculate as 15. It is discovered later on that while calculating the average one number , namely 36 was wrongly read as 26. The correct average is ?









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    New sum of number = previous sum - 26 + 36
    =10 x 15 - 26 + 36
    = 160

    Correct Option: C

    New sum of numbers = previous sum - 26 + 36
    =10 x 15 - 26 + 36
    = 160
    ∴ Correct Average = 160 / 10 = 16.


  1. The average of 13 result is 68. The average of first seven is 63 and that of the last seven is 70 , the seventh result is ?









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    Seventh Result = sum of first 7 results + sum of last 7 results - sum of all 13 results.

    Correct Option: A

    Seventh Result = sum of first 7 results + sum of last 7 results - sum of all 13 results.
    ⇒ Seventh Result = (7 x 63) + (7 x 70) - (13 x 68 )
    =47



  1. The average of 25 results is 18, that of first twelve is 14 and of last twelve is 17 . Thirteenth result is?









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    Thirteenth Result = sum of all 25 results - sum of first 12 results - sum of last 12 results.

    Correct Option: C

    Thirteenth Result = sum of all 25 results - sum of first 12 results - sum of last 12 results.
    = 25 x 18 - 12 x 14 – 12 x 17
    =78


  1. The average temperature of Monday, Tuesday, Wednesday, and Thursday was 38° C and that of Tuesday, Wednesday, Thursday and Friday was 40° C, if the temperature on Monday was 30° C, the temperature of Friday was?









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    Given
    M + T + W + TH = 4 x 38° = 152°
    T + W + TH + F = 4 x 40° = 160°
    M = 30°

    Correct Option: C

    From question
    M + T + W + TH = 4 x 38° = 152°
    ⇒ T + W + TH =152° – 30° = 122°

    Again from question
    ⇒ T + W + TH + F = 4 x 40° = 160°
    ⇒ F = 160° – 122°
    = 38°



  1. The average of 5 consecutive number is n , if the next two number are also include, the average of 7 number will ?









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    Sum of 5 consecutive integers
    x + ( x +1 ) + ( x +2 ) + ( x + 3 ) + ( x +4 ) = 5n
    ⇒ 5x + 10 = 5n
    ⇒ x = ( n – 2 ) ......(i)

    Average of 7 consecutive integers
    = [( 5x + 10 ) + ( x + 5 ) + ( x + 6 )] / 7
    = 7x + 21 / 7
    = x + 3 .....(ii)

    Correct Option: B

    Sum of 5 consecutive integers
    x + ( x +1 ) + ( x +2 ) + ( x + 3 ) + ( x +4 ) = 5n
    ⇒ 5x + 10 = 5n
    ⇒ x = ( n – 2 ) ......(i)

    Average of 7 consecutive integers
    = [( 5x + 10 ) + ( x + 5 ) + ( x + 6 )] / 7
    = 7x + 21 / 7
    = x + 3 .....(ii)

    from eq. (i) and (ii)
    New average = x + 3 = ( n – 2 + 3 ) = n + 1
    So , the new average increases by 1 .