Question

Class A has 9 pupils and class B has 24 pupils.

Both classes sit the same maths test.
The mean score for class A is 40.
The mean score for class B is 20.
What is the mean score (rounded to 2 DP) in the maths test across both classes?

Answer 1

mean ≈ 25.45

Explanation:

mean is calculated as

mean =
`(sum)/(count)`

We require the sum for both classes

class A

mean =
`(sum)/(9)` = 40 ( multiply both sides by 9 )

sum = 9 × 40 = 360

class B

mean =
`(sum)/(24)` = 20 ( multiply both sides by 24

sum = 24 × 20 = 480

Total sum for both classes = 360 + 480 = 840 , then mean for both classes is

mean =
`(840)/(33)` ≈ 25.45 ( to 2 dec. places )