The ratio of white to grey stamps that Julie had was 5 : 2. The cost of each of the white stamps was $5 and the cost of each of the grey stamps was $10. Julie sold 60% of the white stamps and the total cost of the unsold stamps was $270. How many grey stamps did she have left?
| |
White stamps |
Grey stamps |
| Before |
5 u |
2 u |
| Change |
- 3 u |
|
| After |
2 u |
2 u |
Number of white stamps sold
= 60% x 5 u
=
60100 x 5 u
= 3 u
| |
White stamps |
Grey stamps |
Total |
| Number |
2 u |
2 u |
|
| Value |
$5 |
$10 |
|
| Total value |
10 u |
20 u |
$270 |
Total cost of unsold stamps
= 10 u + 20 u
= 30 u
30 u = 270
1 u = 270 ÷ 30 = 9
Number of grey stamps that Julie had left
= 20 u
= 20 x 9
= 180
Answer(s): 180
