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:

84

Average = \(\frac{sum\;of\;no.}{total\;no.}\)

Let the sum of all 10 numbers is = n

⇒ ATQ,

⇒  Average = \(\frac{n}{10}\) = 7

⇒ n = 70    --- (i)

Now each number is multiplied by 12

New sum of no.'s = 12 × n

                          =  12 × 70 = 840

New average = \(\frac{840}{10}\) = 84

Alternate: 

*If old set of numbers is multiply by 'x', then the new average will be 'x' times of old average.*

Therefore,

⇒ New Average = 12 × 7 = 84