The mean score of 3 students in a test out of 25 is 18. Two new students lake the test. What is the lowest marks that can be obtained by one newcomer who scores less than the other one for the overall average of the five students to rise to 20?

The mean score of 3 students in a test out of 25 is 18.

After two students take the test the new average rises to 20

Let marks of two students be x and y

$$\frac{18\times 3 + x+y}{5}= 20$$

$$x+y = 100- 54 = 46$$

Total scored by these two new comers is 46.

In order for one newcomer who scores less than the other one for the overall average of the five students to rise to 20

So if one students score$$x= 21$$ the other has to score $$y=25$$.

So the Lowest score is 21.

Option B is correct.