⁷₈ of Oscar's savings comprised of 5-cent coins and 20-cent coins. Oscar used some 5-cent coins to purchase a frisbee. The number of 20-cent coins left was 40% more than the number of 5-cent coins left. Given that Oscar had 30 more 20-cent coins than 5-cent coins left in the end, find the amount of money Oscar spent on the frisbee.

	5-cent coins	20-cent coins
Before	7x7 = 49 u	1x7 = 7 u
Change	- 44 u
After	5x1 = 5 u	7x1 = 7 u

Fraction of Oscar's savings that comprised of 20-cent coins
= 1 - ⁷₈
= ¹₈

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 5-cent coins
= 7 u - 5 u
= 2 u

2 u = 30

1 u = 30 ÷ 2 = 15

Number of 5-cent coins spent on the frisbee 
= 49 u - 5 u
= 44 u
= 44 x 15
= 660

Amount that Oscar spent on the frisbee 
= 660 x 0.05
= $33

Answer(s): $33