Mark had 6 times as many marbles as Owen at first. Then each of them bought an equal number of new marbles. In the end, Owen had 15 marbles and Mark had 3 times as many marbles as Owen. How many marbles did both of them buy altogether?
| |
Mark |
Owen |
Difference |
| Before |
6x2 =
12 u |
1x2 =
2 u |
5x2 =
10 u |
| Change |
+ ? |
+ ? |
|
| After |
3x5 =
15 u |
1x5 =
5 u |
2x5 =
10 u |
The difference in the number of marbles at first and in the end remains unchanged. Make the difference in the number of marbles at first and in the end the same. LCM of 5 and 2 is 10.
Number of marbles that Owen had in the end = 5 u
5 u = 15
1 u = 15 ÷ 5 = 3
Number of marbles that Mark bought
= 15 u - 12 u
= 3 u
Number of marbles that both of them bought altogether
= 2 x 3 u
= 6 u
= 6 x 3
= 18
Answer(s): 18
