Billy has 10-cent coins and 50-cent coins. The total value of all his coins is $30. He has 12 less 10-cent coins than 50-cent coins. How many coins does he have altogether?
| |
10-cent |
50-cent |
Total |
| Number |
1 u |
1 u + 12 |
2 u + 12 |
| Value |
10 |
50 |
|
| Total value |
10 u |
50 u + 600 |
60 u + 600 |
$1 = 100¢
$30 = 30 x 100 = 3000¢
Billy has 12 more 50-cent coins than 10-cent coins.
Number of 10-cent coins = 1 u
Number of 50-cent coins = 1 u + 12
Total value of 10-cent coins
= 10 x 1 u
= 10 u
Total value of 50-cent coins
= 50 x (1 u + 12)
= 50 u + 600
Total value of the coins
= 10 u + 50 u + 600
= 60 u + 600
60 u + 600 = 3000
60 u = 3000 - 600
60 u = 2400
1 u = 2400 ÷ 60 = 40
Total number of coins
= 1 u + (1 u + 12)
= 2 u + 12
= 2 x 40 + 12
= 80 + 12
= 92
Answer(s): 92
