The number of ten-cent coins in a bag was ¹₄ the number of twenty-cent coins. Fred took out 16 twenty-cent coins and exchanged them for ten-cent coins. Then he put the money back into the bag. The number of twenty-cent coins became ²₅ the number of ten-cent coins. How much money was there in the bag?

	Make u the same (1)x4 = (3)	10-cent (1)	20-cent (2)
Before	4 u	1 u	4 u
Change	+ 128	+ 32	- 16
After	20 p	5 p	2 p

Value of 20-cent coins to be exchanged to 10-cent coins
= 16 x 20
= 320

Number of 10-cent coins to be exchanged from the 20-cent coins
= 320 ÷ 10
= 32

(3) = (2)
20 p - 128 = 2 p + 16
20 p - 2 p = 16 + 128
18 p = 144

1 p = 144 ÷ 18 = 8

Number of 10-cent coins in the end
= 5 p
= 5 p x 8
= 40

Value of 10-cent coins in the end
= 40 x 10
= 400¢

Number of 20-cent coins in the end
= 2 p
= 2 x 8
= 16

Value of 20-cent coins in the end
= 16 x 20
= 320¢

Total value of coins
= 400 + 320
= 720¢

$1 = 100¢
720¢ = $7.20 

Answer(s): $7.20