⁵₇ of Paul's savings comprised of 10-cent coins and 20-cent coins. Paul 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 Paul had 80 more 20-cent coins than 10-cent coins left in the end, find the amount of money Paul spent on the yoyo.

	10-cent coins	20-cent coins
Before	5x7 = 35 u	2x7 = 14 u
Change	- 25 u
After	5x2 = 10 u	7x2 = 14 u

Fraction of Paul's savings that comprised of 20-cent coins
= 1 - ⁵₇
= ²₇

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 2 and 7 is 14.

Number of more 20-cent coins than 10-cent coins
= 14 u - 10 u
= 4 u

4 u = 80

1 u = 80 ÷ 4 = 20

Number of 10-cent coins spent on the yoyo 
= 35 u - 10 u
= 25 u
= 25 x 20
= 500

Amount that Paul spent on the yoyo 
= 500 x 0.1
= $50

Answer(s): $50