Pierre has a total of 20 twenty-cent and ten-cent coins. The total value of the coins is $3. If he spends all the twenty-cent coins on a file, how much does the file cost?
Number of
twenty-cent coins |
Value of
twenty-cent coins |
Number of
ten-cent coins |
Value of
ten-cent coins |
Total
value |
| 20 |
20 x 20
= 400¢ |
0 |
0 |
400¢ |
| 19 |
19 x 20
= 380¢ |
1 |
1 x 10
= 10¢ |
390¢ |
| 10 |
10 x 20
= 200¢ |
10 |
10 x 10
= 100¢ |
300¢ |
$1 = 100¢
$3 = 300¢
Total value if all the coins are twenty-cent coins
= 20 x 20
= 400¢
Big difference between the value of twenty-cent coins and ten-cent coins
= 400 - 300
= 100¢
Small difference between the value of one twenty-cent coin and one ten-cent coin
= 20 - 10
= 10¢
Number of ten-cent coins
= 100 ÷ 10
= 10
Number of twenty-cent coins
= 20 - 10
= 10
Cost of the file
= 10 x 20
= 200¢
= $2
Answer(s): $2
