Roshel saved two coins every day from Monday to Sunday by putting them into a piggy bank. Each coin was either a 10¢ or 50¢ coin. The total value of the coins at the end of 3 weeks was $11.40. 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¢ |
18
|
18 x 50¢ = 900¢ |
24
|
24 x 10¢ = 240¢ |
1140¢ |
$1 = 100¢
$11.40 = 1140¢
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 - 1140
= 960¢
Small difference between the value of one 50¢ coin and one 10¢ coin
= 50 - 10
= 40¢
Number of 10¢ coins
= 960 ÷ 40
= 24
Number of 50¢ coins
= 42 - 24
= 18
Answer(s): 18