Adam has 30 blue marbles and 190 green marbles.
After buying the same number of marbles,
the ratio of the blue marbles and the green marbles becomes 3 : 7.
How many marbles does he buy?
|
Blue |
Green |
Difference |
Before |
30 |
190 |
160 |
Change |
+ ? |
+ ? |
|
After |
3 u |
7 u |
4 u |
At first
Difference in the number of marbles
= 190 - 30
= 160
In the end
Number of blue marbles = 3 u
Number of green marbles = 7 u
Difference in the number of marbles in units
= 7 u - 3 u
= 4 u
The difference in the number of marbles between the blue marbles and the green marbles remains unchanged.
4 u = 160
1 u = 160 ÷ 4 = 40
Number of blue marbles that Adam buys
= 3 u - 30
= 3 x 40 - 30
= 120 - 30
= 90
Total number of marbles that Adam buys
= 2 x 90
= 180
Answer(s): 180