Mrs Chen gave Mary and Risa some money each on Thursday. On Friday, Mary gave
15 of the amount she had to Risa. On Saturday, Risa gave
13 of the amount she had to Mary. In the end, Mary had $55 and Risa had $22. How much did Risa had more than Mary at first?
| |
Mary |
Risa |
Total |
| Before 1 |
5 u |
? |
$77 |
| Change 1 |
- 1 u |
+ 1 u |
|
| After 1 |
4 u |
3 p |
$77 |
| Before 2 |
$55 - 1 p |
3 p |
$77 |
| Change 2 |
+ 1 p |
- 1 p |
|
After 2 |
$55 |
2 p
($22) |
$77 |
Amount that Risa had in the end = 2 p
2 p = 22
1 p = 22 ÷ 2 = 11
Working backwards.
Amount that Mary had after giving to Risa on Friday
= 55 - 1 p
= 55 - 11
= $44
4 u = 44
1 u = 44 ÷ 4 = 11
Amount that Mary had at first
= 5 u
= 5 x 11
= $55
Total amount that Mary and Risa had
= 55 + 22
= $77
Amount that Risa had at first
= 77 - 55
= $22
Amount that Mary had more than Risa
= 55 - 22
= $33
Answer(s): $33
