The ratio of green to grey stamps that Zoe had was 5 : 2. The cost of each of the green stamps was $5 and the cost of each of the grey stamps was $8. Zoe sold 60% of the green stamps and the total cost of the unsold stamps was $78. How many green stamps did she have left?
| |
Green stamps |
Grey stamps |
| Before |
5 u |
2 u |
| Change |
- 3 u |
|
| After |
2 u |
2 u |
Number of green stamps sold
= 60% x 5 u
=
60100 x 5 u
= 3 u
| |
Green stamps |
Grey stamps |
Total |
| Number |
2 u |
2 u |
|
| Value |
$5 |
$8 |
|
| Total value |
10 u |
16 u |
$78 |
Total cost of unsold stamps
= 10 u + 16 u
= 26 u
26 u = 78
1 u = 78 ÷ 26 = 3
Number of green stamps that Zoe had left
= 10 u
= 10 x 3
= 30
Answer(s): 30
