Mr. Ram has a beaker containing M millimeters of solution to distribute to the students in his class. If he gives each student 4 millimeters of solution, he will have 5 millimeters left over. In order to give each student 5 millimeters of solution, He will need an additional 21 millimeters. How many students are there in the class?

- 16
- 21
- 23
- 26

Solution:

**Choice D is correct.**

Let S be the number of students in the class.

According to the question, we have

M – 4S = 5 and 5S = M + 21.

By substituting M = 5 +4S in the second equation, we have

5S = 5 + 4S + 21

Or S = 26.