23 students are on the playground. 18 students are in the library. How many students are there in all?

The correct answer is: 41

No. of students in the playground = 23
No. of students in the library = 18
Total number of students by partial sum method = 23 + 18
To find partial sums add the digits in tens place and ones place seperately.
Partial sum of 23 + 18
Step 1 : Add digits in tens and ones place seperately:
20                                    03
+ 10                   and        + 08

_____                             ______
30                                        11
Thus, Total students =  the sum of 23 + 18 are 30 + 11 = 41.