Zara, Gabby and Eva had 972 marbles. Gabby won some of the marbles from Zara and as a result, Gabby's marbles increased by 50%. Eva then won some marbles from Gabby and Eva's marbles increased by 40%. Finally, Eva lost some of her marbles to Zara and Zara's marbles increased by 20%. In the end, they realised that they each had an equal number of marbles. How many percent less did Zara have in the end than what she had at first? Correct your answer to 1 decimal place.

Zara	Gabby	Eva
972
	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 = 972

1 group = 972 ÷ 3 = 324

1 group = 6 boxes
6 boxes = 324

1 box = 324 ÷ 6 = 54

1 group + 1 box = 7 p
324 + 54 = 7 p
7 p = 378

1 p = 378 ÷ 7 = 54

2 p = 2 x 54 = 108

1 group + 2 p = 3 u
324 + 108 = 3 u
3 u = 432

1 u = 432 ÷ 3 = 144

Number of marbles that Zara had at first
= 5 boxes + 1 u
= (5 x 54) + 144
= 270 + 144
= 414

Percent that Zara had less in the end than at first
= ^{414 - 324}₄₁₄ x 100%
≈ 21.7%

Answer(s): 21.7%