Nick has a total of 17 fifty-cent and twenty-cent coins. The total value of the coins is $7. If he spends all the fifty-cent coins on a stapler, how much does the stapler cost?
Number of
fifty-cent coins |
Value of
fifty-cent coins |
Number of
twenty-cent coins |
Value of
twenty-cent coins |
Total
value |
| 17 |
17 x 50
= 850¢ |
0 |
0 |
850¢ |
| 16 |
16 x 50
= 800¢ |
1 |
1 x 20
= 20¢ |
820¢ |
| 12 |
12 x 50
= 600¢ |
5 |
5 x 20
= 100¢ |
700¢ |
$1 = 100¢
$7 = 700¢
Total value if all the coins are fifty-cent coins
= 17 x 50
= 850¢
Big difference between the value of fifty-cent coins and twenty-cent coins
= 850 - 700
= 150¢
Small difference between the value of one fifty-cent coin and one twenty-cent coin
= 50 - 20
= 30¢
Number of twenty-cent coins
= 150 ÷ 30
= 5
Number of fifty-cent coins
= 17 - 5
= 12
Cost of the stapler
= 12 x 50
= 600¢
= $6
Answer(s): $6
