The ratio of red to purple stamps that Penelope had was 5 : 3. The cost of each of the red stamps was $5 and the cost of each of the purple stamps was $7. Penelope sold 20% of the red stamps and the total cost of the unsold stamps was $164. How many red stamps did she have left?
| |
Red stamps |
Purple stamps |
| Before |
5 u |
3 u |
| Change |
- 1 u |
|
| After |
4 u |
3 u |
Number of red stamps sold
= 20% x 5 u
=
20100 x 5 u
= 1 u
| |
Red stamps |
Purple stamps |
Total |
| Number |
4 u |
3 u |
|
| Value |
$5 |
$7 |
|
| Total value |
20 u |
21 u |
$164 |
Total cost of unsold stamps
= 20 u + 21 u
= 41 u
41 u = 164
1 u = 164 ÷ 41 = 4
Number of red stamps that Penelope had left
= 20 u
= 20 x 4
= 80
Answer(s): 80
