The following are the marks of 15 students out of 50 in an exam: 20, 22, 26, 31, 40, 19, 17, 19, 25, 29, 23, 17, 24, 21, and 35.

Find the median of the marks.

Given data: 20, 22, 26, 31, 40, 19, 17, 19, 25, 29, 23, 17, 24, 21, 35

By arranging the given data in ascending order, we get:

17, 17, 19, 19, 20, 21, 22, 23, 24, 25, 26, 29, 31, 35, 40

The number of terms is n = 15

So, the number of observations is 15 (that is odd).

We know that when n is odd:

→ Median = $\mathbf{\left(}\frac{\mathbf{n}\mathbf{ }\mathbf{+}\mathbf{ }\mathbf{1}}{\mathbf{2}}\mathbf{\right)}$th observation 

Now, by substituting the values, we get:

→ Median = $\frac{(15 + 1)}{2}$th observation

→ Median = 8th observation

→ Median = 23

Hence, the median is 23.