The number of five-cent coins in a bag was
13 the number of ten-cent coins. Tim took out 15 ten-cent coins and exchanged them for five-cent coins. Then he put the money back into the bag. The number of ten-cent coins became
38 the number of five-cent coins. How much money was there in the bag?
|
Make u the same (1)x3 = (3) |
5-cent (1) |
10-cent (2) |
Before |
3 u |
1 u |
3 u |
Change |
+ 90 |
+ 30 |
- 15 |
After |
24 p |
8 p |
3 p |
Value of 10-cent coins to be exchanged to 5-cent coins
= 15 x 10
= 150
Number of 5-cent coins to be exchanged from the 10-cent coins
= 150 ÷ 5
= 30
(3) = (2)
24 p - 90 = 3 p + 15
24 p - 3 p = 15 + 90
21 p = 105
1 p = 105 ÷ 21 = 5
Number of 5-cent coins in the end
= 8 p
= 8 p x 5
= 40
Value of 5-cent coins in the end
= 40 x 5
= 200¢
Number of 10-cent coins in the end
= 3 p
= 3 x 5
= 15
Value of 10-cent coins in the end
= 15 x 10
= 150¢
Total value of coins
= 200 + 150
= 350¢
$1 = 100¢
350¢ = $3.50
Answer(s): $3.50