Question

The average of 7 boys is 15 years one more boys join then and the average age now becomes 14 years. Find the age of the boy who joins last.


Please calculate in easy form​

Answer 1

Answer:

Age of boy who join them in end is 7 years

Step-by-step explanation:

Total number of boys = 7

Average age of boys = 15 years

We know( formula ),

Average = ( sum of quantities ) / ( number of quantities )

∴ 15 years = ( sum of ages of 7 boys in years ) / 7

= > 15 x 7 = sum of ages of 7 boys

= > 105 = sum of ages of 7 boys ...( i )

Now,

Another boy join them and the average age becomes 14 years.

Let present age of the boy who join be "a" years

According to the question : -

= > 14 years = ( sum of ages of 7 boys + age of 8th boy { in years } ) / 8

= > 14 x 8 = ( sum of ages of 7 boys + a )

= > 112 = sum of ages of 7 boys + a

From ( i ),substituting the value of sum of ages of 7 boys

= > 112 = 105 + a

= > 112 - 105 = a

= > 7 = a

Therefor the age of boy who join them in end is 7 years.