Adam has 70 red marbles and 210 blue marbles.
After buying the same number of marbles,
the ratio of the red marbles and the blue marbles becomes 3 : 8.
How many marbles does he buy?
|
Red |
Blue |
Difference |
Before |
70 |
210 |
140 |
Change |
+ ? |
+ ? |
|
After |
3 u |
8 u |
5 u |
At first
Difference in the number of marbles
= 210 - 70
= 140
In the end
Number of red marbles = 3 u
Number of blue marbles = 8 u
Difference in the number of marbles in units
= 8 u - 3 u
= 5 u
The difference in the number of marbles between the red marbles and the blue marbles remains unchanged.
5 u = 140
1 u = 140 ÷ 5 = 28
Number of red marbles that Adam buys
= 3 u - 70
= 3 x 28 - 70
= 84 - 70
= 14
Total number of marbles that Adam buys
= 2 x 14
= 28
Answer(s): 28