Question

In a nursery class of 18 pupils, the average is 4
`(1)/(2)`

years. What is the sum of the ages of pupils?​

Answer 1

81

Explanation:

Average = 4.5 years

Total = 18

Sum = 4.5 × 18 = 81

Answer 2

The sum of ages of all 18 pupils in the class = 81

Explanation:

Total number of pupil in the class = 18

Average of years in the class =
`4(1)/(2)`

Now,
`4(1)/(2)  = 4 + (1)/(2)  = 4 + 0.5 = 4.5`

⇒Average of sum of ages in the class = 4.05

Let us assume the sum of ages of all students in the class = m

By the formula for AVERAGE:

`\textrm{Average of n obseravtions}  = \frac{\textrm{Sum of n observations}}{\textrm{n}}`

`\implies 4.5 = (m)/(18)`

or, m = 18 x 4.5 = 81

Hence, the sum of ages of all 18 pupils in the class = 81