³₅ of Ian's savings comprised of 10-cent coins and 50-cent coins. Ian used some 10-cent coins to purchase a mini plane. The number of 50-cent coins left was 50% more than the number of 10-cent coins left. Given that Ian had 16 more 50-cent coins than 10-cent coins left in the end, find the amount of money Ian spent on the mini plane.

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

Fraction of Ian'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 10-cent coins
= 6 u - 4 u
= 2 u

2 u = 16

1 u = 16 ÷ 2 = 8

Number of 10-cent coins spent on the mini plane 
= 9 u - 4 u
= 5 u
= 5 x 8
= 40

Amount that Ian spent on the mini plane 
= 40 x 0.1
= $4

Answer(s): $4