Eva saved two coins every day from Monday to Sunday by putting them into a tin can. Each coin was either a 10¢ or 50¢ coin. The total value of the coins at the end of 4 weeks was $10.80. How many of the coins were 50¢ coins?
| 50¢ |
Value of 50¢ |
10¢ |
Value of 10¢ |
Total value |
56
|
56 x 50¢ =
2800¢ |
0 |
0 x 10¢ =
0 |
2800¢ |
55
|
55 x 50¢ =
2750¢ |
1 |
1 x 10¢ =
10¢ |
2760¢ |
13
|
13 x 50¢ =
650¢ |
43
|
43 x 10¢ =
430¢ |
1080¢ |
$1 = 100¢
$10.80 = 1080¢
Number of coins in one week
= 2 x 7
= 14
Number of coins in 4 weeks
= 4 x 14
= 56
Total amount saved if all the coins were 50¢
= 56 x 50
= 2800¢
Big difference between the total values of 50¢ coins and 10¢ coins
= 2800 - 1080
= 1720¢
Small difference between the value of one 50¢ coin and one 10¢ coin
= 50 - 10
= 40¢
Number of 10¢ coins
= 1720 ÷ 40
= 43
Number of 50¢ coins
= 56 - 43
= 13
Answer(s): 13
