Question

the average age of 7 boys is 15 years another boy join them and the average age becomes 14 years now .find the age of age boy who join them in end

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.

Answer 2

Answer:

7 is the correct answer

hope it's helpful