The ratio of the number of blue stamps to red stamps is 7 : 2. After Luke gives away 30 blue stamps and buys another 40 red stamps, there is equal number of blue stamps and red stamps. How many stamps does Luke have now?
| |
Blue |
Red |
| Before |
7 u |
2 u |
| Change |
- 30 |
+ 40 |
| After |
7 u - 30 |
2 u + 40 |
The number of blue stamps and red stamps in the end is the same.
7 u - 30 = 2 u + 40
7 u - 2 u = 40 + 30
5 u = 70
1 u = 70 ÷ 5 = 14
Number of stamps that Luke has now
= 7 u - 30 + 2 u + 40
= 7 u + 2 u - 30 + 40
= 9 u + 10
= 9 x 14 + 10
= 126 + 10
= 136
Answer(s): 136
