There were a total of thirty-one 10-cent coins and 20-cent coins in a bag. Given that the total amount of money in the bag was $5.10. 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 |
31
|
31 x 20
= 620¢ |
0
|
0
|
620¢
|
30
|
30 x 20
= 600¢ |
1
|
1 x 10
= 10¢ |
610¢
|
20
|
20 x 20
= 400¢ |
11
|
11 x 10
= 110¢ |
510¢ |
$1 = 100¢
$5.10 = 510¢
Amount in the bag if all are 20-cent coins
= 31 x 20
= 620¢
Big difference between the value of 20-cent coins and 10-cent coins
= 620 - 510
= 110¢
Small difference between the value of one 20-cent coin and one 10-cent coin
= 20 - 10
= 10¢
Number of 10-cent coins
= 110 ÷ 10
= 11
Answer(s): 11
