There are 21 classrooms at Pine School. There are 33 students in each room. The total number of students in school is?

The correct answer is: 693

Here , we have to find the total number of student in school.
Firstly , we have 21 classrooms, each classrooms have 33 students.
Then ,
1 classroom = 33 students
To find 21 bus, we have to multiply 21 to both sides,
1 x 21 row = 21 x 33 students
We know that the total number of student can drive altogether are 21 x 33, to solve this multiplication we are using partial product rule,
According to partial product,
We can write 21 as 20 and 1, and 33 as 30 and 3 , we separate the ones digit and tens digit. Now by partial product, we have:
20 x 30 = 600
30 x 1 = 30
20 x 3 = 60
1 x 3 = 3
Now add all the partial product of find the solution.
21 x 33 = 600 + 30 + 60 + 3
21 x 33 = 693
Therefore, the total number of student in school are 693.
The correct answer is 693 (option (b)) .
Or,
Total class rooms = 21
Each room = 33 students
Total number of students in the class = 21 x 33 = 693

Here 21 classrooms and each classroom having 33 students  , multiply both of them for solution. For multiplication you can use any method , and one of them are partial product , which break your product and makes it easy to solve. Apply same type of concept in similar questions.