Oliver had 25% more stickers than Zoe. Lily had 50% fewer stickers than Oliver. Oliver and Zoe gave Lily some stickers in the ratio of 3 : 5. As a result, Lily had 60% more stickers than before. Given that Lily had 30 more stickers than Zoe in the end, how many stickers did Oliver give to Lily?

Oliver	Zoe	Lily
5x2	4x2
2x5		1x5
10	8	5

100% + 25% = 125%
125% = ¹²⁵₁₀₀ = ⁵₄

Oliver : Zoe = 5 : 4

100% - 50% = 50%
50% = ⁵⁰₁₀₀ = ¹₂

Oliver : Lily = 2 : 1

The number of stickers that Oliver had at first is repeated. Make the number of stickers that Oliver had at first the same.  LCM of 5 and 2 is 10.

	Oliver	Zoe	Lily
Before	10x8 =  80 u	8x8 = 64 u	5x8 = 40 u
Change			+ 3x8 = + 24 u
Comparing the changes in the number of stickers	- 3x3 = - 9 u	- 5x3 = - 15 u	+ 8x3 = + 24 u
After	71 u	49 u	8x8 = 64 u

60% x 5 
= ⁶⁰₁₀₀ x 5 
= 3 

The total number of stickers that Oliver and Zoe gave to Lily is repeated.  Make the total number of stickers that Oliver and Zoe gave to Lily the same.  LCM of 8 and 3 is 24.

Number of stickers that Lily had more than Zoe 
= 64 u - 49 u
= 15 u

15 u = 30

1 u = 30 ÷ 15 = 2

Number of stickers that Oliver gave to Lily
= 9 u
= 9 x 2
= 18

Answer(s): 18