Joelle, Usha and Winnie had 918 stamps. Usha won some of the stamps from Joelle and as a result, Usha's stamps increased by 50%. Winnie then won some stamps from Usha and Winnie's stamps increased by 40%. Finally, Winnie lost some of her stamps to Joelle and Joelle's stamps increased by 20%. In the end, they realised that they each had an equal number of stamps. How many percent less did Joelle have in the end than what she had at first? Correct your answer to 1 decimal place.

Joelle	Usha	Winnie
918
	2 u
- 1 u	+ 1 u
	3 u
		5 p
	- 2 p	+ 2 p
		7 p
5 boxes
+ 1 box		- 1 box
6 boxes
1 group	1 group	1 group

50% = ⁵⁰₁₀₀ = ¹₂
40% = ⁴⁰₁₀₀ = ²₅
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

2 p = 2 x 51 = 102

1 group + 2 p = 3 u
306 + 102 = 3 u
3 u = 408

1 u = 408 ÷ 3 = 136

Number of stamps that Joelle had at first
= 5 boxes + 1 u
= (5 x 51) + 136
= 255 + 136
= 391

Percent that Joelle had less in the end than at first
= ^{391 - 306}₃₉₁ x 100%
≈ 21.7%

Answer(s): 21.7%