Adam has 80 blue marbles.
He has 4 times as many blue marbles as red marbles.
After he buys an equal number of blue and red marbles,
the number of blue marbles is 3 times that of the red marbles.
- How many blue marbles are there in the end?
- How many red marbles are there in the end?
- How many marbles are there in the end?
- How many marbles does Adam buy?
|
Blue marbles |
Red marbles |
Difference |
Before |
4 x 2 = 8 u |
1 x 2 = 2 u |
3 x 2 = 6 u |
Change |
+ ? |
+ ? |
|
After |
3 x 3 = 9 u |
1 x 3 = 3 u |
2 x 3 = 6 u |
(a)
The difference in the number between the blue and red marbles at first and in the end remains unchanged.
LCM of 3 and 2 is 6.
8 u = 80
1 u = 80 ÷ 8 = 10
Number of blue marbles in the end
= 9 u
= 9 x 10
= 90
(b)
Number of red marbles in the end
= 3 u
= 3 x 10
= 30
(c)
Total number of marbles in the end
= 90 + 30
= 120
(d)
Total number of marbles that Adam buys
= (9 u - 8 u) x 2
= 1 u x 2
= 2 u
= 2 x 10
= 20
Answer(s): (a) 90; (b) 30; (c) 120; (d) 20