Adam has 90 blue marbles and 270 red marbles.
After buying the same number of marbles,
the ratio of the blue marbles and the red marbles becomes 2 : 5.
How many marbles does he buy?
|
Blue |
Red |
Difference |
Before |
90 |
270 |
180 |
Change |
+ ? |
+ ? |
|
After |
2 u |
5 u |
3 u |
At first
Difference in the number of marbles
= 270 - 90
= 180
In the end
Number of blue marbles = 2 u
Number of red marbles = 5 u
Difference in the number of marbles in units
= 5 u - 2 u
= 3 u
The difference in the number of marbles between the blue marbles and the red marbles remains unchanged.
3 u = 180
1 u = 180 ÷ 3 = 60
Number of blue marbles that Adam buys
= 2 u - 90
= 2 x 60 - 90
= 120 - 90
= 30
Total number of marbles that Adam buys
= 2 x 30
= 60
Answer(s): 60