The ratio of red to white stamps that Shiyun had was 5 : 3. The cost of each of the red stamps was $4 and the cost of each of the white stamps was $8. Shiyun sold 20% of the red stamps and the total cost of the unsold stamps was $320. How many white stamps did she have left?
| |
Red stamps |
White 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 |
White stamps |
Total |
| Number |
4 u |
3 u |
|
| Value |
$4 |
$8 |
|
| Total value |
16 u |
24 u |
$320 |
Total cost of unsold stamps
= 16 u + 24 u
= 40 u
40 u = 320
1 u = 320 ÷ 40 = 8
Number of white stamps that Shiyun had left
= 24 u
= 24 x 8
= 192
Answer(s): 192
