George has 10-cent coins and 20-cent coins. The total value of all his coins is $40. He has 17 less 10-cent coins than 20-cent coins. How many coins does he have altogether?
| |
10-cent |
20-cent |
Total |
| Number |
1 u |
1 u + 17 |
2 u + 17 |
| Value |
10 |
20 |
|
| Total value |
10 u |
20 u + 340 |
30 u + 340 |
$1 = 100¢
$40 = 40 x 100 = 4000¢
George has 17 more 20-cent coins than 10-cent coins.
Number of 10-cent coins = 1 u
Number of 20-cent coins = 1 u + 17
Total value of 10-cent coins
= 10 x 1 u
= 10 u
Total value of 20-cent coins
= 20 x (1 u + 17)
= 20 u + 340
Total value of the coins
= 10 u + 20 u + 340
= 30 u + 340
30 u + 340 = 4000
30 u = 4000 - 340
30 u = 3660
1 u = 3660 ÷ 30 = 122
Total number of coins
= 1 u + (1 u + 17)
= 2 u + 17
= 2 x 122 + 17
= 244 + 17
= 261
Answer(s): 261
