The ratio of black to blue stamps that Vanessa had was 5 : 3. The cost of each of the black stamps was $3 and the cost of each of the blue stamps was $4. Vanessa sold 20% of the black stamps and the total cost of the unsold stamps was $216. How many black stamps did she have left?
|
Black stamps |
Blue stamps |
Before |
5 u |
3 u |
Change |
- 1 u |
|
After |
4 u |
3 u |
Number of black stamps sold
= 20% x 5 u
=
20100 x 5 u
= 1 u
|
Black stamps |
Blue stamps |
Total |
Number |
4 u |
3 u |
|
Value |
$3 |
$4 |
|
Total value |
12 u |
12 u |
$216 |
Total cost of unsold stamps
= 12 u + 12 u
= 24 u
24 u = 216
1 u = 216 ÷ 24 = 9
Number of black stamps that Vanessa had left
= 12 u
= 12 x 9
= 108
Answer(s): 108