Albert has 5-cent coins and 10-cent coins. The total value of all his coins is $12. He has 15 less 5-cent coins than 10-cent coins. How many coins does he have altogether?
| |
5-cent |
10-cent |
Total |
| Number |
1 u |
1 u + 15 |
2 u + 15 |
| Value |
5 |
10 |
|
| Total value |
5 u |
10 u + 150 |
15 u + 150 |
$1 = 100¢
$12 = 12 x 100 = 1200¢
Albert has 15 more 10-cent coins than 5-cent coins.
Number of 5-cent coins = 1 u
Number of 10-cent coins = 1 u + 15
Total value of 5-cent coins
= 5 x 1 u
= 5 u
Total value of 10-cent coins
= 10 x (1 u + 15)
= 10 u + 150
Total value of the coins
= 5 u + 10 u + 150
= 15 u + 150
15 u + 150 = 1200
15 u = 1200 - 150
15 u = 1050
1 u = 1050 ÷ 15 = 70
Total number of coins
= 1 u + (1 u + 15)
= 2 u + 15
= 2 x 70 + 15
= 140 + 15
= 155
Answer(s): 155
