Opal, Zoe and Victoria had 972 stamps. Zoe won some of the stamps from Opal and as a result, Zoe's stamps increased by 25%. Victoria then won some stamps from Zoe and Victoria's stamps increased by 50%. Finally, Victoria lost some of her stamps to Opal and Opal's stamps increased by 20%. In the end, they realised that they each had an equal number of stamps. How many percent less did Opal have in the end than what she had at first? Correct your answer to 1 decimal place.

Opal	Zoe	Victoria
972
	4 u
- 1 u	+ 1 u
	5 u
		2 p
	- 1 p	+ 1 p
		3 p
5 boxes
+ 1 box		- 1 box
6 boxes
1 group	1 group	1 group

25% = ²⁵₁₀₀ = ¹₄
50% = ⁵⁰₁₀₀ = ¹₂
20% = ²⁰₁₀₀ = ¹₅

Working backwards.

3 groups = 972

1 group = 972 ÷ 3 = 324

1 group = 6 boxes
6 boxes = 324

1 box = 324 ÷ 6 = 54

1 group + 1 box = 3 p
324 + 54 = 3 p
3 p = 378

1 p = 378 ÷ 3 = 126

1 p = 1 x 126 = 126

1 group + 1 p = 5 u
324 + 126 = 5 u
5 u = 450

1 u = 450 ÷ 5 = 90

Number of stamps that Opal had at first
= 5 boxes + 1 u
= (5 x 54) + 90
= 270 + 90
= 360

Percent that Opal had less in the end than at first
= ^{360 - 324}₃₆₀ x 100%
≈ 10.0%

Answer(s): 10.0%