Question

the average age of the class is 15 yrs. the average age of boys and girls is 13 and 16 years respectively.if the no. of girls is 18 the number of boys in the class​

Answer 1

Answer:

9 boys

Step-by-step explanation:

total age of girls + total age of boys / total no. of students = average

Answer 2

Answer:

9

Step-by-step explanation:

Concept= Average

Given= Total average of class, Individual average of girls and boys, Number of girls

To find= Number of Boys

Explanation=

We know that average of the whole class is 15years.

Average of Boys is 13years.

Average of girls is 16 years.

Number of Girls is 18.

so, the total age of girls is Average of girls*number of girls= 16*18= 288years.

Let the total number of boys be x.

Total age of boys is Average of boys*Number of boys= 13*x= 13x years.

Total number of boys and girls= x+18

Average of class= 15

We know ,

Average age of class=

(total age of boys + total age of girls)/Total number of boys and girls

=> 15=(13x + 288)/(x+18)

=> 15x + 270= 13x + 288

=> 2x= 18

=> x= 9

Therefore the number of boys is 9.

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