⁶₇ of Oliver's savings comprised of 20-cent coins and 50-cent coins. Oliver used some 20-cent coins to purchase a toy car. The number of 50-cent coins left was 40% more than the number of 20-cent coins left. Given that Oliver had 10 more 50-cent coins than 20-cent coins left in the end, find the amount of money Oliver spent on the toy car.

	20-cent coins	50-cent coins
Before	6x7 = 42 u	1x7 = 7 u
Change	- 37 u
After	5x1 = 5 u	7x1 = 7 u

Fraction of Oliver's savings that comprised of 50-cent coins
= 1 - ⁶₇
= ¹₇

Number of 50-cents coins in the end in percentage
= 100% + 40%
= 140%

140% = ¹⁴⁰₁₀₀ = ⁷₅

Number of 50-cent coins remains unchanged. Make the number of 50-cent coins the same.  LCM of 1 and 7 is 7.

Number of more 50-cent coins than 20-cent coins
= 7 u - 5 u
= 2 u

2 u = 10

1 u = 10 ÷ 2 = 5

Number of 20-cent coins spent on the toy car 
= 42 u - 5 u
= 37 u
= 37 x 5
= 185

Amount that Oliver spent on the toy car 
= 185 x 0.2
= $37

Answer(s): $37