The ratio of red to white stamps that Diana had was 4 : 3. The cost of each of the red stamps was $4 and the cost of each of the white stamps was $6. Diana sold 25% of the red stamps and the total cost of the unsold stamps was $150. How many white stamps did she have left?
| |
Red stamps |
White stamps |
| Before |
4 u |
3 u |
| Change |
- 1 u |
|
| After |
3 u |
3 u |
Number of red stamps sold
= 25% x 4 u
=
25100 x 4 u
= 1 u
| |
Red stamps |
White stamps |
Total |
| Number |
3 u |
3 u |
|
| Value |
$4 |
$6 |
|
| Total value |
12 u |
18 u |
$150 |
Total cost of unsold stamps
= 12 u + 18 u
= 30 u
30 u = 150
1 u = 150 ÷ 30 = 5
Number of white stamps that Diana had left
= 18 u
= 18 x 5
= 90
Answer(s): 90
