The number of five-cent coins in a pouch was
15 the number of twenty-cent coins. Luke took out 15 twenty-cent coins and exchanged them for five-cent coins. Then he put the money back into the pouch. The number of twenty-cent coins became
58 the number of five-cent coins. How much money was there in the pouch?
|
Make u the same (1)x5 = (3) |
5-cent (1) |
20-cent (2) |
Before |
5 u |
1 u |
5 u |
Change |
+ 300 |
+ 60 |
- 15 |
After |
40 p |
8 p |
5 p |
Value of 20-cent coins to be exchanged to 5-cent coins
= 15 x 20
= 300
Number of 5-cent coins to be exchanged from the 20-cent coins
= 300 ÷ 5
= 60
(3) = (2)
40 p - 300 = 5 p + 15
40 p - 5 p = 15 + 300
35 p = 315
1 p = 315 ÷ 35 = 9
Number of 5-cent coins in the end
= 8 p
= 8 p x 9
= 72
Value of 5-cent coins in the end
= 72 x 5
= 360¢
Number of 20-cent coins in the end
= 5 p
= 5 x 9
= 45
Value of 20-cent coins in the end
= 45 x 20
= 900¢
Total value of coins
= 360 + 900
= 1260¢
$1 = 100¢
1260¢ = $12.60
Answer(s): $12.60