Irene, Marion and Jane had 630 marbles. Marion won some of the marbles from Irene and as a result, Marion's marbles increased by 50%. Jane then won some marbles from Marion and Jane's marbles increased by 40%. Finally, Jane lost some of her marbles to Irene and Irene's marbles increased by 25%. In the end, they realised that they each had an equal number of marbles. How many percent less did Irene have in the end than what she had at first? Correct your answer to 1 decimal place.

Irene	Marion	Jane
630
	2 u
- 1 u	+ 1 u
	3 u
		5 p
	- 2 p	+ 2 p
		7 p
4 boxes
+ 1 box		- 1 box
5 boxes
1 group	1 group	1 group

50% = ⁵⁰₁₀₀ = ¹₂
40% = ⁴⁰₁₀₀ = ²₅
25% = ²⁵₁₀₀ = ¹₄

Working backwards.

3 groups = 630

1 group = 630 ÷ 3 = 210

1 group = 5 boxes
5 boxes = 210

1 box = 210 ÷ 5 = 42

1 group + 1 box = 7 p
210 + 42 = 7 p
7 p = 252

1 p = 252 ÷ 7 = 36

2 p = 2 x 36 = 72

1 group + 2 p = 3 u
210 + 72 = 3 u
3 u = 282

1 u = 282 ÷ 3 = 94

Number of marbles that Irene had at first
= 4 boxes + 1 u
= (4 x 42) + 94
= 168 + 94
= 262

Percent that Irene had less in the end than at first
= ^{262 - 210}₂₆₂ x 100%
≈ 19.8%

Answer(s): 19.8%