Cathy's and Shiyun's savings were in the ratio of 4 : 7. Both of them shared the cost of their older brother's gift equally. Cathy's remaining savings was ¹₅ as much as Shiyun's savings. What percentage of her savings did Cathy spend? Correct the answer to 1 decimal place.

	Cathy	Shiyun	Difference
Before	4x4 = 16 u	7x4 = 28 u	3x4 = 12 u
Change	- 13 u	- 13 u
After	1x3 = 3 u	5x3 = 15 u	4x3 = 12 u

Since Cathy and Shiyun shared the cost of their older brother's gift equally, the amount each paid for the gift is the same. 

So, the difference in the amounts between Cathy and Shiyun at first and in the end remains the same.  Make the difference in the amounts between Cathy and Shiyun at first and in the end the same. LCM of 3 and 4 is 12.

Amount that Cathy spent on the gift
= 16 u - 3 u
= 13 u

Percentage of her savings that Cathy spent
= ¹³₁₆ x 100%
≈ 81.3%

Answer(s): 81.3%