Three girls, Xuan, Marion and Fiona had a total of 1920 stamps. Some exchanges were made. First, Xuan gave Marion as many stamps as Marion had. After that, Marion gave
13 of whatever she had then to Fiona. Finally, Fiona gave
13 of whatever she had to Xuan. As a result, they each had the same number of stamps. How many stamps did Xuan have at first?
|
Xuan |
Marion |
Fiona |
Total |
Before 1 |
? |
1 u |
|
1920 |
Change 1 |
- 1 u |
+ 1 u |
|
|
After 1 |
|
2 u |
|
|
Before 2 |
|
3 p |
|
1920 |
Change 2 |
|
- 1 p |
+ 1 p |
|
After 2 |
|
2 p |
|
|
Before 3 |
|
|
3 boxes |
1920 |
Change 3 |
+ 1 box |
|
- 1 box |
|
After 3 |
|
|
2 boxes |
|
After 3 |
1 group |
1 group |
1 group |
1920 |
3 groups = 1920
1 group = 1920 ÷ 3 = 640
1 group = 2 boxes 2 boxes = 640
1 box = 640 ÷ 2 = 320
2 p = 1 group
1 p = 640 ÷ 2 = 320
3 p = 3 x 320 = 960
3 p = 2 u
2 u = 960
1 u = 960 ÷ 2 = 480
Number of stamps that Xuan had at first
= 1 group - 1 box + 1 u
= 640 - 320 + 480
= 800
Answer(s): 800