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The average of ten numbers is 7. If each number is multiplied by 12, then the average of the new set of numbers will be:
82
84
7
19
84
When every term in a set is multiplied by a constant 'k', the new average is simply the old average multiplied by that same constant 'k'. Here, 7 ├Ч 12 = 84.
The average of ten numbers is 7. Each number is multiplied by 12.
AnewтАЛ=AoldтАЛ├Чk
When every term in a set is multiplied by a constant 'k', the new average is simply the old average multiplied by that same constant 'k'. Here, 7 ├Ч 12 = 84.
Students sometimes try to calculate the sum of the numbers first (10 ├Ч 7 = 70), then multiply the sum by 12 (70 ├Ч 12 = 840), and then divide by 10, which is correct but unnecessarily time-consuming.
Identify given average
The original average of the 10 numbers is given as 7.
AoldтАЛ=7
Apply transformation rule
According to the properties of averages, if every number in a dataset is multiplied by a constant k, the average of the new set is the product of the original average and k. Here, k=12.
AnewтАЛ=7├Ч12
Calculate the result
Multiplying the average by the constant yields the final value.
AnewтАЛ=84
B is correct because multiplying each number by 12 results in the average being multiplied by 12, giving 7├Ч12=84.
This property applies to all linear operations: if you add c to each number, the average increases by c. If you multiply by k, the average is multiplied by k.