Mary bought some stamps. She gave
13 of the stamps to her brother and sold
25 of the remaining stamps. After that, she bought another 72 stamps and had the same number of stamps that she bought at first. How many stamps did Mary buy at first?
| Her brother |
Remaining stamps |
Bought stamps |
Total |
1x5 =
5 u |
2x5 =
10 u |
|
3x5 =
15 u |
| |
Sold |
Left |
|
|
| |
2x2 |
3x2 |
|
|
| 5 u |
4 u |
6 u |
72 |
|
The remaining number of stamps before Mary bought another 72 stamps is repeated. Make the remaining number of stamps the same. LCM of 2 and 5 is 10.
Total number of stamps at first = 15 u
Number of stamps that Mary had left and bought after that = 6 u + 72
15 u = 6 u + 72
15 u - 6 u = 72
9 u = 72
1 u = 72 ÷ 9 = 8
Total number of stamps at first
= 15 u
= 15 x 8
= 120
Answer(s): 120
