Opal bought some stamps. She gave
13 of the stamps to her sister and sold
35 of the remaining stamps. After that, she bought another 99 stamps and had the same number of stamps that she bought at first. How many stamps did Opal buy at first?
| Her sister |
Remaining stamps |
Bought stamps |
Total |
1x5 =
5 u |
2x5 =
10 u |
|
3x5 =
15 u |
| |
Sold |
Left |
|
|
| |
3x2 |
2x2 |
|
|
| 5 u |
6 u |
4 u |
99 |
|
The remaining number of stamps before Opal bought another 99 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 Opal had left and bought after that = 4 u + 99
15 u = 4 u + 99
15 u - 4 u = 99
11 u = 99
1 u = 99 ÷ 11 = 9
Total number of stamps at first
= 15 u
= 15 x 9
= 135
Answer(s): 135
