Ivory, Lucy and Shiyun had 918 stamps. Lucy won some of the stamps from Ivory and as a result, Lucy's stamps increased by 50%. Shiyun then won some stamps from Lucy and Shiyun's stamps increased by 75%. Finally, Shiyun lost some of her stamps to Ivory and Ivory's stamps increased by 20%. In the end, they realised that they each had an equal number of stamps. How many percent less did Ivory have in the end than what she had at first? Correct your answer to 1 decimal place.

Ivory	Lucy	Shiyun
918
	2 u
- 1 u	+ 1 u
	3 u
		4 p
	- 3 p	+ 3 p
		7 p
5 boxes
+ 1 box		- 1 box
6 boxes
1 group	1 group	1 group

50% = ⁵⁰₁₀₀ = ¹₂
75% = ⁷⁵₁₀₀ = ³₄
20% = ²⁰₁₀₀ = ¹₅

Working backwards.

3 groups = 918

1 group = 918 ÷ 3 = 306

1 group = 6 boxes
6 boxes = 306

1 box = 306 ÷ 6 = 51

1 group + 1 box = 7 p
306 + 51 = 7 p
7 p = 357

1 p = 357 ÷ 7 = 51

3 p = 3 x 51 = 153

1 group + 3 p = 3 u
306 + 153 = 3 u
3 u = 459

1 u = 459 ÷ 3 = 153

Number of stamps that Ivory had at first
= 5 boxes + 1 u
= (5 x 51) + 153
= 255 + 153
= 408

Percent that Ivory had less in the end than at first
= ^{408 - 306}₄₀₈ x 100%
≈ 25.0%

Answer(s): 25.0%