Tom has 5-cent coins and 10-cent coins. The total value of all his coins is $36. He has 9 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 + 9 |
2 u + 9 |
| Value |
5 |
10 |
|
| Total value |
5 u |
10 u + 90 |
15 u + 90 |
$1 = 100¢
$36 = 36 x 100 = 3600¢
Tom has 9 more 10-cent coins than 5-cent coins.
Number of 5-cent coins = 1 u
Number of 10-cent coins = 1 u + 9
Total value of 5-cent coins
= 5 x 1 u
= 5 u
Total value of 10-cent coins
= 10 x (1 u + 9)
= 10 u + 90
Total value of the coins
= 5 u + 10 u + 90
= 15 u + 90
15 u + 90 = 3600
15 u = 3600 - 90
15 u = 3510
1 u = 3510 ÷ 15 = 234
Total number of coins
= 1 u + (1 u + 9)
= 2 u + 9
= 2 x 234 + 9
= 468 + 9
= 477
Answer(s): 477
