The number of five-cent coins in a jar was
13 the number of twenty-cent coins. Caden took out 21 twenty-cent coins and exchanged them for five-cent coins. Then he put the money back into the jar. The number of twenty-cent coins became
25 the number of five-cent coins. How much money was there in the jar?
|
Make u the same (1)x3 = (3) |
5-cent (1) |
20-cent (2) |
Before |
3 u |
1 u |
3 u |
Change |
+ 252 |
+ 84 |
- 21 |
After |
15 p |
5 p |
2 p |
Value of 20-cent coins to be exchanged to 5-cent coins
= 21 x 20
= 420
Number of 5-cent coins to be exchanged from the 20-cent coins
= 420 ÷ 5
= 84
(3) = (2)
15 p - 252 = 2 p + 21
15 p - 2 p = 21 + 252
13 p = 273
1 p = 273 ÷ 13 = 21
Number of 5-cent coins in the end
= 5 p
= 5 p x 21
= 105
Value of 5-cent coins in the end
= 105 x 5
= 525¢
Number of 20-cent coins in the end
= 2 p
= 2 x 21
= 42
Value of 20-cent coins in the end
= 42 x 20
= 840¢
Total value of coins
= 525 + 840
= 1365¢
$1 = 100¢
1365¢ = $13.65
Answer(s): $13.65