Ian and Japheth had 90 pens. After Ian gave 21 pens to Japheth. Japheth, in return, gave half of his pens to Ian. In the end, Ian had twice as many pens as Japheth. How many pens did Ian have at first?
| |
Ian |
Japheth |
Total |
| Before |
1 u + 21 |
2 u - 21 |
90 |
| Change 1 |
- 21 |
+ 21 |
|
| After 1 |
1 u |
2 u |
|
| Change 2 |
+ 1 u |
- 1 u |
|
| After 2 |
2 u |
1 u |
90 |
Total number of pens that Ian and Japheth had at first and in the end remains unchanged.
Total number of pens
= 2 u + 1 u
= 3 u
1 u = 90 ÷ 3 = 30
Number of pens that Ian had at first
= 1 u + 21
= 30 + 21
= 51
Answer(s): 51
