The number of five-cent coins in a bag was
14 the number of twenty-cent coins. David took out 18 twenty-cent coins and exchanged them for five-cent coins. Then he put the money back into the bag. The number of twenty-cent coins became
25 the number of five-cent coins. How much money was there in the bag?
|
Make u the same (1)x4 = (3) |
5-cent (1) |
20-cent (2) |
Before |
4 u |
1 u |
4 u |
Change |
+ 288 |
+ 72 |
- 18 |
After |
20 p |
5 p |
2 p |
Value of 20-cent coins to be exchanged to 5-cent coins
= 18 x 20
= 360
Number of 5-cent coins to be exchanged from the 20-cent coins
= 360 ÷ 5
= 72
(3) = (2)
20 p - 288 = 2 p + 18
20 p - 2 p = 18 + 288
18 p = 306
1 p = 306 ÷ 18 = 17
Number of 5-cent coins in the end
= 5 p
= 5 p x 17
= 85
Value of 5-cent coins in the end
= 85 x 5
= 425¢
Number of 20-cent coins in the end
= 2 p
= 2 x 17
= 34
Value of 20-cent coins in the end
= 34 x 20
= 680¢
Total value of coins
= 425 + 680
= 1105¢
$1 = 100¢
1105¢ = $11.05
Answer(s): $11.05