Billy has 7 more 50-cent coins than 10-cent coins. After he used 11 of his 50-cent coins, the total value of 50-cent coins is $3.60 more than the total value of 10-cent coins. How many coins did he have at first?
|
50¢ |
10¢ |
Before |
1 u + 7 |
1 u |
Change |
- 11 |
|
After |
1 u - 4 |
1 u |
|
50¢ |
10¢ |
Number |
1 u - 4 |
1 u |
Value |
50 |
10 |
Total value |
50 u - 200 |
10 u |
$1 = 100¢
$3.60 = 360¢
Number of 50¢ coins in the end
= 1 u + 7 - 11
= 1 u - 4
Total value of 50¢ coins in the end
= 50 x (1 u - 4)
= 50 u - 200
Total value of 10¢ coins in the end
= 10 x 1 u
= 10 u
After using 11 50-cent coins, the value of 50-cent coins is 360¢ more than the value of 10-cent coins. If another 360¢ is added to the 10-cent coins, the total value of 50-cent coins and 10-cent coins will be the same.
50 u - 200 = 10 u + 360
50 u - 10 u = 360 + 200
40 u = 560
1 u = 560 ÷ 40 = 14
Number of coins that Billy had at first
= 1 u + 1 u + 7
= 2 u + 7
= (2 x 14) + 7
= 28 + 7
= 35
Answer(s): 35