³₅ of Justin's savings comprised of 5-cent coins and 10-cent coins. Justin used some 5-cent coins to purchase a marble. The number of 10-cent coins left was 40% more than the number of 5-cent coins left. Given that Justin had 80 more 10-cent coins than 5-cent coins left in the end, find the amount of money Justin spent on the marble.

	5-cent coins	10-cent coins
Before	3x7 = 21 u	2x7 = 14 u
Change	- 11 u
After	5x2 = 10 u	7x2 = 14 u

Fraction of Justin's savings that comprised of 10-cent coins
= 1 - ³₅
= ²₅

Number of 10-cents coins in the end in percentage
= 100% + 40%
= 140%

140% = ¹⁴⁰₁₀₀ = ⁷₅

Number of 10-cent coins remains unchanged. Make the number of 10-cent coins the same.  LCM of 2 and 7 is 14.

Number of more 10-cent coins than 5-cent coins
= 14 u - 10 u
= 4 u

4 u = 80

1 u = 80 ÷ 4 = 20

Number of 5-cent coins spent on the marble 
= 21 u - 10 u
= 11 u
= 11 x 20
= 220

Amount that Justin spent on the marble 
= 220 x 0.05
= $11

Answer(s): $11