The ratio of the number of red cards to green cards is 3 : 1. After Julian gives away 20 red cards and buys another 30 green cards, there is equal number of red cards and green cards. How many cards does Julian have now?
|
Red |
Green |
Before |
3 u |
1 u |
Change |
- 20 |
+ 30 |
After |
3 u - 20 |
1 u + 30 |
The number of red cards and green cards in the end is the same.
3 u - 20 = 1 u + 30
3 u - 1 u = 30 + 20
2 u = 50
1 u = 50 ÷ 2 = 25
Number of cards that Julian has now
= 3 u - 20 + 1 u + 30
= 3 u + 1 u - 20 + 30
= 4 u + 10
= 4 x 25 + 10
= 100 + 10
= 110
Answer(s): 110