Usha saved two coins every day from Monday to Sunday by putting them into a glass jar. Each coin was either a 10¢ or 20¢ coin. The total value of the coins at the end of 6 weeks was $11.60. How many of the coins were 20¢ coins?
| 20¢ |
Value of 20¢ |
10¢ |
Value of 10¢ |
Total value |
84
|
84 x 20¢ =
1680¢ |
0 |
0 x 10¢ =
0 |
1680¢ |
83
|
83 x 20¢ =
1660¢ |
1 |
1 x 10¢ =
10¢ |
1670¢ |
32
|
32 x 20¢ =
640¢ |
52
|
52 x 10¢ =
520¢ |
1160¢ |
$1 = 100¢
$11.60 = 1160¢
Number of coins in one week
= 2 x 7
= 14
Number of coins in 6 weeks
= 6 x 14
= 84
Total amount saved if all the coins were 20¢
= 84 x 20
= 1680¢
Big difference between the total values of 20¢ coins and 10¢ coins
= 1680 - 1160
= 520¢
Small difference between the value of one 20¢ coin and one 10¢ coin
= 20 - 10
= 10¢
Number of 10¢ coins
= 520 ÷ 10
= 52
Number of 20¢ coins
= 84 - 52
= 32
Answer(s): 32
