The ratio of green to yellow stamps that Gwen had was 5 : 2. The cost of each of the green stamps was $1 and the cost of each of the yellow stamps was $2. Gwen sold 20% of the green stamps and the total cost of the unsold stamps was $80. How many yellow stamps did she have left?
| |
Green stamps |
Yellow stamps |
| Before |
5 u |
2 u |
| Change |
- 1 u |
|
| After |
4 u |
2 u |
Number of green stamps sold
= 20% x 5 u
=
20100 x 5 u
= 1 u
| |
Green stamps |
Yellow stamps |
Total |
| Number |
4 u |
2 u |
|
| Value |
$1 |
$2 |
|
| Total value |
4 u |
4 u |
$80 |
Total cost of unsold stamps
= 4 u + 4 u
= 8 u
8 u = 80
1 u = 80 ÷ 8 = 10
Number of yellow stamps that Gwen had left
= 4 u
= 4 x 10
= 40
Answer(s): 40
