1) D

Number of pupils in year 4 = 120 – (24 + 40 + 16 + 24) = 16
Total number of girls = 48
Total number of boys = 120 – 48 = 72

There is a 1 in 12 chance that a boy selected at random is in Year 4.
Let the number of boys in year 4 = ‘N’

1/12 = N/72
N = 72/12 = 6
So there are 6 boys in Year 4.

We know the total number of pupils in Year 4 is 16.

Probability of that year 4 pupil selected at random is a boys = 6/16 = 3/8
Probability = 3 in 8
So the answer is D

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