Riordan has a total of 14 fifty-cent and ten-cent coins. The total value of the coins is $3. 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
ten-cent coins |
Value of
ten-cent coins |
Total
value |
| 14 |
14 x 50
= 700¢ |
0 |
0 |
700¢ |
| 13 |
13 x 50
= 650¢ |
1 |
1 x 10
= 10¢ |
660¢ |
| 4 |
4 x 50
= 200¢ |
10 |
10 x 10
= 100¢ |
300¢ |
$1 = 100¢
$3 = 300¢
Total value if all the coins are fifty-cent coins
= 14 x 50
= 700¢
Big difference between the value of fifty-cent coins and ten-cent coins
= 700 - 300
= 400¢
Small difference between the value of one fifty-cent coin and one ten-cent coin
= 50 - 10
= 40¢
Number of ten-cent coins
= 400 ÷ 40
= 10
Number of fifty-cent coins
= 14 - 10
= 4
Cost of the pen
= 4 x 50
= 200¢
= $2
Answer(s): $2
