Zane has a total of 18 fifty-cent and twenty-cent coins. The total value of the coins is $6. If he spends all the fifty-cent coins on a pen, how much does the pen cost?
Number of
fifty-cent coins |
Value of
fifty-cent coins |
Number of
twenty-cent coins |
Value of
twenty-cent coins |
Total
value |
| 18 |
18 x 50
= 900¢ |
0 |
0 |
900¢ |
| 17 |
17 x 50
= 850¢ |
1 |
1 x 20
= 20¢ |
870¢ |
| 8 |
8 x 50
= 400¢ |
10 |
10 x 20
= 200¢ |
600¢ |
$1 = 100¢
$6 = 600¢
Total value if all the coins are fifty-cent coins
= 18 x 50
= 900¢
Big difference between the value of fifty-cent coins and twenty-cent coins
= 900 - 600
= 300¢
Small difference between the value of one fifty-cent coin and one twenty-cent coin
= 50 - 20
= 30¢
Number of twenty-cent coins
= 300 ÷ 30
= 10
Number of fifty-cent coins
= 18 - 10
= 8
Cost of the pen
= 8 x 50
= 400¢
= $4
Answer(s): $4
