Oliver has 5-cent coins and 20-cent coins. The total value of all his coins is $37. He has 15 less 5-cent coins than 20-cent coins. How many coins does he have altogether?
| |
5-cent |
20-cent |
Total |
| Number |
1 u |
1 u + 15 |
2 u + 15 |
| Value |
5 |
20 |
|
| Total value |
5 u |
20 u + 300 |
25 u + 300 |
$1 = 100¢
$37 = 37 x 100 = 3700¢
Oliver has 15 more 20-cent coins than 5-cent coins.
Number of 5-cent coins = 1 u
Number of 20-cent coins = 1 u + 15
Total value of 5-cent coins
= 5 x 1 u
= 5 u
Total value of 20-cent coins
= 20 x (1 u + 15)
= 20 u + 300
Total value of the coins
= 5 u + 20 u + 300
= 25 u + 300
25 u + 300 = 3700
25 u = 3700 - 300
25 u = 3400
1 u = 3400 ÷ 25 = 136
Total number of coins
= 1 u + (1 u + 15)
= 2 u + 15
= 2 x 136 + 15
= 272 + 15
= 287
Answer(s): 287
