Question

The average age of 5 students is 9 years . out of them the ages of 4 students are 5,7,8 and 15 years .what is the age of the remaining students.​

Answer 1

10 years

Explanation:

Let the age of the remaining student be x years.

`Average \:of\:ages = (Sum \: of \: ages )/(No. \: of \: students) \\ \\ 9 = (5 + 7 + 8 + 15 + x)/(5) \\ \\ 9 = (35+ x)/(5) \\ \\ 9 * 5 = 35 + x \\ \\ 45 = 35 + x \\ \\ 45 - 35 = x \\ \\ x = 10 \: years`

Answer 2

The age of the remaining student = 10 years

Explanation:

Let the age of the remaining student = x

Average age of 5 students = 9 year

Sum of the age of 5 students = 9*5 = 45 years

5 + 7 + 8 + 15 + x = 45

35 + x = 45

x = 45 - 35

x = 10

The age of the remaining student = 10 years