Mary and Zoe have some files in the ratio 3 : 7. Mary has 84 less files than Zoe. How many files must Zoe give to Mary so that they will have the same number of files?
| |
Mary |
Zoe |
Total |
| Before |
3 u |
7 u |
10 u |
| Change |
+ 2 u |
- 2 u |
|
After |
1x5 =
5 u |
1x5 =
5 u |
2x5 =
10 u |
The total number of files remains unchanged. Make the total number of files at first and in the end the same. LCM of 2 and 10 is 10.
Difference in the number of files at first
= 7 u - 3 u
= 4 u
4 u = 84
1 u = 84 ÷ 4 = 21
Number of files that each of them had in the end
= 10 u ÷ 2
= 5 u
Number of files that Zoe must give to Mary
= 5 u - 3 u
= 2 u
= 2 x 21
= 42
Answer(s): 42
