Adam has 72 blue marbles.
He has 6 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 5 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 |
6 x 4 = 24 u |
1 x 4 = 4 u |
5 x 4 = 20 u |
Change |
+ ? |
+ ? |
|
After |
5 x 5 = 25 u |
1 x 5 = 5 u |
4 x 5 = 20 u |
(a)
The difference in the number between the blue and red marbles at first and in the end remains unchanged.
LCM of 5 and 4 is 20.
24 u = 72
1 u = 72 ÷ 24 = 3
Number of blue marbles in the end
= 25 u
= 25 x 3
= 75
(b)
Number of red marbles in the end
= 5 u
= 5 x 3
= 15
(c)
Total number of marbles in the end
= 75 + 15
= 90
(d)
Total number of marbles that Adam buys
= (25 u - 24 u) x 2
= 1 u x 2
= 2 u
= 2 x 3
= 6
Answer(s): (a) 75; (b) 15; (c) 90; (d) 6