The ratio of gold to black stamps that Raeann had was 5 : 3. The cost of each of the gold stamps was $4 and the cost of each of the black stamps was $7. Raeann sold 60% of the gold stamps and the total cost of the unsold stamps was $87. How many black stamps did she have left?
| |
Gold stamps |
Black stamps |
| Before |
5 u |
3 u |
| Change |
- 3 u |
|
| After |
2 u |
3 u |
Number of gold stamps sold
= 60% x 5 u
=
60100 x 5 u
= 3 u
| |
Gold stamps |
Black stamps |
Total |
| Number |
2 u |
3 u |
|
| Value |
$4 |
$7 |
|
| Total value |
8 u |
21 u |
$87 |
Total cost of unsold stamps
= 8 u + 21 u
= 29 u
29 u = 87
1 u = 87 ÷ 29 = 3
Number of black stamps that Raeann had left
= 21 u
= 21 x 3
= 63
Answer(s): 63
