Brandon had 5 times as many marbles as Justin at first. Then each of them bought an equal number of new marbles. In the end, Justin had 20 marbles and Brandon had 3 times as many marbles as Justin. How many marbles did both of them buy altogether?
| |
Brandon |
Justin |
Difference |
| Before |
5x1 =
5 u |
1x1 =
1 u |
4x1 =
4 u |
| Change |
+ ? |
+ ? |
|
| After |
3x2 =
6 u |
1x2 =
2 u |
2x2 =
4 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 4 and 2 is 4.
Number of marbles that Justin had in the end = 2 u
2 u = 20
1 u = 20 ÷ 2 = 10
Number of marbles that Brandon bought
= 6 u - 5 u
= 1 u
Number of marbles that both of them bought altogether
= 2 x 1 u
= 2 u
= 2 x 10
= 20
Answer(s): 20
