There were a total of thirty-nine 20-cent coins and 50-cent coins in a bag. Given that the total amount of money in the bag was $13.80. How many 20-cent coins were there in the bag?
Number of 50-cent coins |
Value of 50-cent coins |
Number of 20-cent coins |
Value of 20-cent coins |
Total value |
39
|
39 x 50 = 1950¢ |
0
|
0
|
1950¢
|
38
|
38 x 50 = 1900¢ |
1
|
1 x 20 = 20¢ |
1920¢
|
20
|
20 x 50 = 1000¢ |
19
|
19 x 20 = 380¢ |
1380¢ |
$1 = 100¢
$13.80 = 1380¢
Amount in the bag if all are 50-cent coins
= 39 x 50
= 1950¢
Big difference between the value of 50-cent coins and 20-cent coins
= 1950 - 1380
= 570¢
Small difference between the value of one 50-cent coin and one 20-cent coin
= 50 - 20
= 30¢
Number of 20-cent coins
= 570 ÷ 30
= 19
Answer(s): 19