The ratio of yellow to black stamps that Natalie had was 5 : 3. The cost of each of the yellow stamps was $4 and the cost of each of the black stamps was $8. Natalie sold 20% of the yellow stamps and the total cost of the unsold stamps was $240. How many black stamps did she have left?
| |
Yellow stamps |
Black stamps |
| Before |
5 u |
3 u |
| Change |
- 1 u |
|
| After |
4 u |
3 u |
Number of yellow stamps sold
= 20% x 5 u
=
20100 x 5 u
= 1 u
| |
Yellow stamps |
Black stamps |
Total |
| Number |
4 u |
3 u |
|
| Value |
$4 |
$8 |
|
| Total value |
16 u |
24 u |
$240 |
Total cost of unsold stamps
= 16 u + 24 u
= 40 u
40 u = 240
1 u = 240 ÷ 40 = 6
Number of black stamps that Natalie had left
= 24 u
= 24 x 6
= 144
Answer(s): 144
