Yoko saved two coins every day from Monday to Sunday by putting them into a glass jar. Each coin was either a 10¢ or 50¢ coin. The total value of the coins at the end of 2 weeks was $10.80. How many of the coins were 50¢ coins?
50¢ |
Value of 50¢ |
10¢ |
Value of 10¢ |
Total value |
28
|
28 x 50¢ = 1400¢ |
0 |
0 x 10¢ = 0 |
1400¢ |
27
|
27 x 50¢ = 1350¢ |
1 |
1 x 10¢ = 10¢ |
1360¢ |
20
|
20 x 50¢ = 1000¢ |
8
|
8 x 10¢ = 80¢ |
1080¢ |
$1 = 100¢
$10.80 = 1080¢
Number of coins in one week
= 2 x 7
= 14
Number of coins in 2 weeks
= 2 x 14
= 28
Total amount saved if all the coins were 50¢
= 28 x 50
= 1400¢
Big difference between the total values of 50¢ coins and 10¢ coins
= 1400 - 1080
= 320¢
Small difference between the value of one 50¢ coin and one 10¢ coin
= 50 - 10
= 40¢
Number of 10¢ coins
= 320 ÷ 40
= 8
Number of 50¢ coins
= 28 - 8
= 20
Answer(s): 20