Oliver, Sean and Ahmad had some stamps in the ratio of 2 : 3 : 5. Ahmad gave 40% of his stamps to Oliver and Sean. As a result, Oliver had the same number of stamps as Sean and Ahmad had 16 fewer stamps than Oliver.

1. What was the percentage increase in Oliver's stamps after receiving from Ahmad?
2. How many stamps did Sean have at first?

Oliver	Sean	Ahmad	Total
2 u	3 u	5 u	10 u
+ 2 u		- 2 u
3.5 u	3.5 u	3 u	10 u

(a)
Number of stamps that Ahmad gave away
= 40% x 5
= ⁴⁰₁₀₀ x 5
= 2 u

Number of stamps that Oliver and Sean each had in the end
= (10 u - 3 u) ÷ 2
= 7 u ÷ 2
= 3.5 u

Increase in the number of stamps that Oliver had
= 3.5 u - 2 u
= 1.5 u

Percentage increase in Oliver's stamps after receiving from Ahmad
= ^1.5₂ x 100%
= 75%

(b)
3.5 u = 3 u + 16
3.5 u - 3 u = 16
0.5 u = 16

1 u = 16 ÷ 0.5 = 32

Number of stamps that Sean had at first
= 3 u
= 3 x 32
= 96

Answer(s): (a) 75%; (b) 96