⁹₁₀ of Fred's savings comprised of 10-cent coins and 20-cent coins. Fred used some 10-cent coins to purchase a yoyo. The number of 20-cent coins left was 40% more than the number of 10-cent coins left. Given that Fred had 20 more 20-cent coins than 10-cent coins left in the end, find the amount of money Fred spent on the yoyo.

	10-cent coins	20-cent coins
Before	9x7 = 63 u	1x7 = 7 u
Change	- 58 u
After	5x1 = 5 u	7x1 = 7 u

Fraction of Fred's savings that comprised of 20-cent coins
= 1 - ⁹₁₀
= ¹₁₀

Number of 20-cents coins in the end in percentage
= 100% + 40%
= 140%

140% = ¹⁴⁰₁₀₀ = ⁷₅

Number of 20-cent coins remains unchanged. Make the number of 20-cent coins the same.  LCM of 1 and 7 is 7.

Number of more 20-cent coins than 10-cent coins
= 7 u - 5 u
= 2 u

2 u = 20

1 u = 20 ÷ 2 = 10

Number of 10-cent coins spent on the yoyo 
= 63 u - 5 u
= 58 u
= 58 x 10
= 580

Amount that Fred spent on the yoyo 
= 580 x 0.1
= $58

Answer(s): $58