Risa and Yen have some pens. If Risa gives 15 pens to Yen, Yen will have 4 times the number of pens as Risa. If Yen gives 17 pens to Risa, Risa will have
12 as many pens as Yen. How many pens does Risa have at first?
|
Case 1 |
Case 2 |
|
Risa |
Yen |
Risa |
Yen |
Before |
3 u + 15 |
12 u - 15 |
5 u - 17 |
10 u + 17 |
Change |
- 15 |
+ 15 |
+ 17 |
- 17 |
After |
1x3 = 3 u |
4x3 = 12 u |
1x5 = 5 u |
2x5 = 10 u |
The total number of pens in both cases remains unchanged. Make the total number of pens in both cases the same. LCM of 5 and 3 is 15.
Number of pens that Risa had at first is the same in both cases.
5 u - 17 = 3 u + 15
5 u - 3 u = 15 + 17
2 u = 32
1 u = 16
Number of pens that Risa had at first
= 3 u + 15
= 3 x 16 + 15
= 48 + 15
= 63
Answer(s): 63