Irene bought some pens. She gave
15 of the pens to her sister and sold
25 of the remaining pens. After that, she bought another 143 pens and had the same number of pens that she bought at first. How many pens did Irene buy at first?
| Her sister |
Remaining pens |
Bought pens |
Total |
1x5 =
5 u |
4x5 =
20 u |
|
5x5 =
25 u |
| |
Sold |
Left |
|
|
| |
2x4 |
3x4 |
|
|
| 5 u |
8 u |
12 u |
143 |
|
The remaining number of pens before Irene bought another 143 pens is repeated. Make the remaining number of pens the same. LCM of 4 and 5 is 20.
Total number of pens at first = 25 u
Number of pens that Irene had left and bought after that = 12 u + 143
25 u = 12 u + 143
25 u - 12 u = 143
13 u = 143
1 u = 143 ÷ 13 = 11
Total number of pens at first
= 25 u
= 25 x 11
= 275
Answer(s): 275
