Diana bought some pens. She gave
13 of the pens to her sister and sold
25 of the remaining pens. After that, she bought another 45 pens and had the same number of pens that she bought at first. How many pens did Diana buy at first?
| Her sister |
Remaining pens |
Bought pens |
Total |
1x5 =
5 u |
2x5 =
10 u |
|
3x5 =
15 u |
| |
Sold |
Left |
|
|
| |
2x2 |
3x2 |
|
|
| 5 u |
4 u |
6 u |
45 |
|
The remaining number of pens before Diana bought another 45 pens is repeated. Make the remaining number of pens the same. LCM of 2 and 5 is 10.
Total number of pens at first = 15 u
Number of pens that Diana had left and bought after that = 6 u + 45
15 u = 6 u + 45
15 u - 6 u = 45
9 u = 45
1 u = 45 ÷ 9 = 5
Total number of pens at first
= 15 u
= 15 x 5
= 75
Answer(s): 75
