The ratio of the number of red cards to blue cards is 5 : 3. After Seth gives away 20 red cards and buys another 40 blue cards, there is equal number of red cards and blue cards. How many cards does Seth have now?
| |
Red |
Blue |
| Before |
5 u |
3 u |
| Change |
- 20 |
+ 40 |
| After |
5 u - 20 |
3 u + 40 |
The number of red cards and blue cards in the end is the same.
5 u - 20 = 3 u + 40
5 u - 3 u = 40 + 20
2 u = 60
1 u = 60 ÷ 2 = 30
Number of cards that Seth has now
= 5 u - 20 + 3 u + 40
= 5 u + 3 u - 20 + 40
= 8 u + 20
= 8 x 30 + 20
= 240 + 20
= 260
Answer(s): 260
