The ratio of the number of blue marbles to red marbles is 8 : 5. After Riordan gives away 60 blue marbles and buys another 90 red marbles, there is equal number of blue marbles and red marbles. How many marbles does Riordan have now?
| |
Blue |
Red |
| Before |
8 u |
5 u |
| Change |
- 60 |
+ 90 |
| After |
8 u - 60 |
5 u + 90 |
The number of blue marbles and red marbles in the end is the same.
8 u - 60 = 5 u + 90
8 u - 5 u = 90 + 60
3 u = 150
1 u = 150 ÷ 3 = 50
Number of marbles that Riordan has now
= 8 u - 60 + 5 u + 90
= 8 u + 5 u - 60 + 90
= 13 u + 30
= 13 x 50 + 30
= 650 + 30
= 680
Answer(s): 680
