Last Friday, Tommy had twice as many marbles as John. Today, Tommy gives 15 of his marbles to his best friend. Now, John has thrice as many marbles as Tommy. How many marbles does John have?
| |
Tommy |
John |
| Before |
2x3 =
6 u |
1x3 =
3 u |
| Change |
- 15 |
|
| After |
1 u |
3 u |
The number of marbles that John had at first and in the end remains unchanged. Make the number of marbles that John has the same. LCM of 1 and 3 is 3.
Number of marbles that Tommy gives to his best friend
= 6 u - 1 u
= 5 u
5 u = 15
1 u = 15 ÷ 5 = 3
Number of marbles that John has
= 3 u
= 3 x 3
= 9
Answer(s): 9
