Nora and Xuan have some pens in the ratio 3 : 7. Nora has 40 less pens than Xuan. How many pens must Xuan give to Nora so that they will have the same number of pens?
| |
Nora |
Xuan |
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 pens remains unchanged. Make the total number of pens at first and in the end the same. LCM of 2 and 10 is 10.
Difference in the number of pens at first
= 7 u - 3 u
= 4 u
4 u = 40
1 u = 40 ÷ 4 = 10
Number of pens that each of them had in the end
= 10 u ÷ 2
= 5 u
Number of pens that Xuan must give to Nora
= 5 u - 3 u
= 2 u
= 2 x 10
= 20
Answer(s): 20
