The ratio of white to yellow stamps that Joelle had was 4 : 3. The cost of each of the white stamps was $4 and the cost of each of the yellow stamps was $5. Joelle sold 50% of the white stamps and the total cost of the unsold stamps was $138. How many yellow stamps did she have left?
| |
White stamps |
Yellow stamps |
| Before |
4 u |
3 u |
| Change |
- 2 u |
|
| After |
2 u |
3 u |
Number of white stamps sold
= 50% x 4 u
=
50100 x 4 u
= 2 u
| |
White stamps |
Yellow stamps |
Total |
| Number |
2 u |
3 u |
|
| Value |
$4 |
$5 |
|
| Total value |
8 u |
15 u |
$138 |
Total cost of unsold stamps
= 8 u + 15 u
= 23 u
23 u = 138
1 u = 138 ÷ 23 = 6
Number of yellow stamps that Joelle had left
= 15 u
= 15 x 6
= 90
Answer(s): 90
