Linda saved two coins every day from Monday to Sunday by putting them into a coin box. Each coin was either a 10¢ or 50¢ coin. The total value of the coins at the end of 3 weeks was $13.80. How many of the coins were 50¢ coins?
| 50¢ |
Value of 50¢ |
10¢ |
Value of 10¢ |
Total value |
42
|
42 x 50¢ =
2100¢ |
0 |
0 x 10¢ =
0 |
2100¢ |
41
|
41 x 50¢ =
2050¢ |
1 |
1 x 10¢ =
10¢ |
2060¢ |
24
|
24 x 50¢ =
1200¢ |
18
|
18 x 10¢ =
180¢ |
1380¢ |
$1 = 100¢
$13.80 = 1380¢
Number of coins in one week
= 2 x 7
= 14
Number of coins in 3 weeks
= 3 x 14
= 42
Total amount saved if all the coins were 50¢
= 42 x 50
= 2100¢
Big difference between the total values of 50¢ coins and 10¢ coins
= 2100 - 1380
= 720¢
Small difference between the value of one 50¢ coin and one 10¢ coin
= 50 - 10
= 40¢
Number of 10¢ coins
= 720 ÷ 40
= 18
Number of 50¢ coins
= 42 - 18
= 24
Answer(s): 24
