The ratio of black to red stamps that Gabby had was 5 : 2. The cost of each of the black stamps was $4 and the cost of each of the red stamps was $5. Gabby sold 60% of the black stamps and the total cost of the unsold stamps was $108. How many red stamps did she have left?
| |
Black stamps |
Red stamps |
| Before |
5 u |
2 u |
| Change |
- 3 u |
|
| After |
2 u |
2 u |
Number of black stamps sold
= 60% x 5 u
=
60100 x 5 u
= 3 u
| |
Black stamps |
Red stamps |
Total |
| Number |
2 u |
2 u |
|
| Value |
$4 |
$5 |
|
| Total value |
8 u |
10 u |
$108 |
Total cost of unsold stamps
= 8 u + 10 u
= 18 u
18 u = 108
1 u = 108 ÷ 18 = 6
Number of red stamps that Gabby had left
= 10 u
= 10 x 6
= 60
Answer(s): 60
