Harry has 20-cent coins and 50-cent coins. The total value of all his coins is $40. He has 17 less 20-cent coins than 50-cent coins. How many coins does he have altogether?
| |
20-cent |
50-cent |
Total |
| Number |
1 u |
1 u + 17 |
2 u + 17 |
| Value |
20 |
50 |
|
| Total value |
20 u |
50 u + 850 |
70 u + 850 |
$1 = 100¢
$40 = 40 x 100 = 4000¢
Harry has 17 more 50-cent coins than 20-cent coins.
Number of 20-cent coins = 1 u
Number of 50-cent coins = 1 u + 17
Total value of 20-cent coins
= 20 x 1 u
= 20 u
Total value of 50-cent coins
= 50 x (1 u + 17)
= 50 u + 850
Total value of the coins
= 20 u + 50 u + 850
= 70 u + 850
70 u + 850 = 4000
70 u = 4000 - 850
70 u = 3150
1 u = 3150 ÷ 70 = 45
Total number of coins
= 1 u + (1 u + 17)
= 2 u + 17
= 2 x 45 + 17
= 90 + 17
= 107
Answer(s): 107
