The ratio of purple to red stamps that Shiyun had was 5 : 2. The cost of each of the purple stamps was $5 and the cost of each of the red stamps was $10. Shiyun sold 40% of the purple stamps and the total cost of the unsold stamps was $280. How many purple stamps did she have left?
| |
Purple stamps |
Red stamps |
| Before |
5 u |
2 u |
| Change |
- 2 u |
|
| After |
3 u |
2 u |
Number of purple stamps sold
= 40% x 5 u
=
40100 x 5 u
= 2 u
| |
Purple stamps |
Red stamps |
Total |
| Number |
3 u |
2 u |
|
| Value |
$5 |
$10 |
|
| Total value |
15 u |
20 u |
$280 |
Total cost of unsold stamps
= 15 u + 20 u
= 35 u
35 u = 280
1 u = 280 ÷ 35 = 8
Number of purple stamps that Shiyun had left
= 15 u
= 15 x 8
= 120
Answer(s): 120
