There were a total of thirty-nine 10-cent coins and 20-cent coins in a bag. Given that the total amount of money in the bag was $6.60. How many 10-cent coins were there in the bag?
Number of 20-cent coins |
Value of 20-cent coins |
Number of 10-cent coins |
Value of 10-cent coins |
Total value |
39
|
39 x 20 = 780¢ |
0
|
0
|
780¢
|
38
|
38 x 20 = 760¢ |
1
|
1 x 10 = 10¢ |
770¢
|
27
|
27 x 20 = 540¢ |
12
|
12 x 10 = 120¢ |
660¢ |
$1 = 100¢
$6.60 = 660¢
Amount in the bag if all are 20-cent coins
= 39 x 20
= 780¢
Big difference between the value of 20-cent coins and 10-cent coins
= 780 - 660
= 120¢
Small difference between the value of one 20-cent coin and one 10-cent coin
= 20 - 10
= 10¢
Number of 10-cent coins
= 120 ÷ 10
= 12
Answer(s): 12