JAMB 1986 · UME · Q2

If Musa had scored 75 in Biology instead of 57, his average mark in four subjects would have been 60. What was his total mark?

Worked solution (try it first)

With 75 in Biology the average of 4 subjects is 60, so that total would be $4 \times 60 = 240$ .
His real Biology mark is $75 - 57 = 18$ lower.
So his actual total is $240 - 18 = 222$ , option C.