Peter had 6 times as many marbles as Andy at first. Then each of them bought an equal number of new marbles. In the end, Andy had 20 marbles and Peter had 3 times as many marbles as Andy. How many marbles did both of them buy altogether?
| |
Peter |
Andy |
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 Andy had in the end = 5 u
5 u = 20
1 u = 20 ÷ 5 = 4
Number of marbles that Peter bought
= 15 u - 12 u
= 3 u
Number of marbles that both of them bought altogether
= 2 x 3 u
= 6 u
= 6 x 4
= 24
Answer(s): 24
