The number of ten-cent coins in a jar was
13 the number of twenty-cent coins. Fred took out 24 twenty-cent coins and exchanged them for ten-cent coins. Then he put the money back into the jar. The number of twenty-cent coins became
35 the number of ten-cent coins. How much money was there in the jar?
|
Make u the same (1)x3 = (3) |
10-cent (1) |
20-cent (2) |
Before |
3 u |
1 u |
3 u |
Change |
+ 144 |
+ 48 |
- 24 |
After |
15 p |
5 p |
3 p |
Value of 20-cent coins to be exchanged to 10-cent coins
= 24 x 20
= 480
Number of 10-cent coins to be exchanged from the 20-cent coins
= 480 ÷ 10
= 48
(3) = (2)
15 p - 144 = 3 p + 24
15 p - 3 p = 24 + 144
12 p = 168
1 p = 168 ÷ 12 = 14
Number of 10-cent coins in the end
= 5 p
= 5 p x 14
= 70
Value of 10-cent coins in the end
= 70 x 10
= 700¢
Number of 20-cent coins in the end
= 3 p
= 3 x 14
= 42
Value of 20-cent coins in the end
= 42 x 20
= 840¢
Total value of coins
= 700 + 840
= 1540¢
$1 = 100¢
1540¢ = $15.40
Answer(s): $15.40