³₅ of Riordan's savings comprised of 20-cent coins and 50-cent coins. Riordan used some 20-cent coins to purchase a basketball set. The number of 50-cent coins left was 50% more than the number of 20-cent coins left. Given that Riordan had 40 more 50-cent coins than 20-cent coins left in the end, find the amount of money Riordan spent on the basketball set.

	20-cent coins	50-cent coins
Before	3x3 = 9 u	2x3 = 6 u
Change	- 5 u
After	2x2 = 4 u	3x2 = 6 u

Fraction of Riordan's savings that comprised of 50-cent coins
= 1 - ³₅
= ²₅

Number of 50-cents coins in the end in percentage
= 100% + 50%
= 150%

150% = ¹⁵⁰₁₀₀ = ³₂

Number of 50-cent coins remains unchanged. Make the number of 50-cent coins the same.  LCM of 2 and 3 is 6.

Number of more 50-cent coins than 20-cent coins
= 6 u - 4 u
= 2 u

2 u = 40

1 u = 40 ÷ 2 = 20

Number of 20-cent coins spent on the basketball set 
= 9 u - 4 u
= 5 u
= 5 x 20
= 100

Amount that Riordan spent on the basketball set 
= 100 x 0.2
= $20

Answer(s): $20