Andy, Luke and Harry had some erasers in the ratio of 2 : 3 : 5. Harry gave 40% of his erasers to Andy and Luke. As a result, Andy had the same number of erasers as Luke and Harry had 36 fewer erasers than Andy.

1. What was the percentage increase in Andy's erasers after receiving from Harry?
2. How many erasers did Luke have at first?

Andy	Luke	Harry	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 erasers that Harry gave away
= 40% x 5
= ⁴⁰₁₀₀ x 5
= 2 u

Number of erasers that Andy and Luke each had in the end
= (10 u - 3 u) ÷ 2
= 7 u ÷ 2
= 3.5 u

Increase in the number of erasers that Andy had
= 3.5 u - 2 u
= 1.5 u

Percentage increase in Andy's erasers after receiving from Harry
= ^1.5₂ x 100%
= 75%

(b)
3.5 u = 3 u + 36
3.5 u - 3 u = 36
0.5 u = 36

1 u = 36 ÷ 0.5 = 72

Number of erasers that Luke had at first
= 3 u
= 3 x 72
= 216

Answer(s): (a) 75%; (b) 216