Sean has a total of 19 fifty-cent and twenty-cent coins. The total value of the coins is $8. If he spends all the fifty-cent coins on a notebook, how much does the notebook cost?
Number of
fifty-cent coins |
Value of
fifty-cent coins |
Number of
twenty-cent coins |
Value of
twenty-cent coins |
Total
value |
| 19 |
19 x 50
= 950¢ |
0 |
0 |
950¢ |
| 18 |
18 x 50
= 900¢ |
1 |
1 x 20
= 20¢ |
920¢ |
| 14 |
14 x 50
= 700¢ |
5 |
5 x 20
= 100¢ |
800¢ |
$1 = 100¢
$8 = 800¢
Total value if all the coins are fifty-cent coins
= 19 x 50
= 950¢
Big difference between the value of fifty-cent coins and twenty-cent coins
= 950 - 800
= 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
= 19 - 5
= 14
Cost of the notebook
= 14 x 50
= 700¢
= $7
Answer(s): $7
