The ratio of brown to blue stamps that Fiona had was 4 : 3. The cost of each of the brown stamps was $3 and the cost of each of the blue stamps was $4. Fiona sold 25% of the brown stamps and the total cost of the unsold stamps was $42. How many blue stamps did she have left?
| |
Brown stamps |
Blue stamps |
| Before |
4 u |
3 u |
| Change |
- 1 u |
|
| After |
3 u |
3 u |
Number of brown stamps sold
= 25% x 4 u
=
25100 x 4 u
= 1 u
| |
Brown stamps |
Blue stamps |
Total |
| Number |
3 u |
3 u |
|
| Value |
$3 |
$4 |
|
| Total value |
9 u |
12 u |
$42 |
Total cost of unsold stamps
= 9 u + 12 u
= 21 u
21 u = 42
1 u = 42 ÷ 21 = 2
Number of blue stamps that Fiona had left
= 12 u
= 12 x 2
= 24
Answer(s): 24
