Wendy collects 32 rocks. His sister collects 29 rocks. How many rocks do they collect in all?

The correct answer is: 61

Wendy collects 32 rocks. His sister collects 29 rocks.
Total rocks collected by Wendy and her sister = 32 + 29
To find partial sums add the digits in tens place and ones place seperately.
Partial sum of 32 + 29
Step 1 : Add digits in tens and ones place seperately:
30                                    02
+ 20                   and        + 09

_____                             ______
50                                        11
Thus, the sum of 32 + 29 are 50 + 11 = 61.


So, there are 61 rocks in all.