The ratio of the number of blue stamps to red stamps is 7 : 5. After Cole gives away 20 blue stamps and buys another 50 red stamps, there is equal number of blue stamps and red stamps. How many stamps does Cole have now?
| |
Blue |
Red |
| Before |
7 u |
5 u |
| Change |
- 20 |
+ 50 |
| After |
7 u - 20 |
5 u + 50 |
The number of blue stamps and red stamps in the end is the same.
7 u - 20 = 5 u + 50
7 u - 5 u = 50 + 20
2 u = 70
1 u = 70 ÷ 2 = 35
Number of stamps that Cole has now
= 7 u - 20 + 5 u + 50
= 7 u + 5 u - 20 + 50
= 12 u + 30
= 12 x 35 + 30
= 420 + 30
= 450
Answer(s): 450
