The ratio of green to white stamps that Sarah had was 5 : 3. The cost of each of the green stamps was $3 and the cost of each of the white stamps was $4. Sarah sold 40% of the green stamps and the total cost of the unsold stamps was $105. How many green stamps did she have left?
| |
Green stamps |
White stamps |
| Before |
5 u |
3 u |
| Change |
- 2 u |
|
| After |
3 u |
3 u |
Number of green stamps sold
= 40% x 5 u
=
40100 x 5 u
= 2 u
| |
Green stamps |
White stamps |
Total |
| Number |
3 u |
3 u |
|
| Value |
$3 |
$4 |
|
| Total value |
9 u |
12 u |
$105 |
Total cost of unsold stamps
= 9 u + 12 u
= 21 u
21 u = 105
1 u = 105 ÷ 21 = 5
Number of green stamps that Sarah had left
= 9 u
= 9 x 5
= 45
Answer(s): 45
