Position of Chetan from the left in a row of students is 16, whereas the position of Rajni sitting in the same row is 15th from the right. After interchanging their positions, the position of the Chetan becomes 17th from the left. What is the total number of students in the row?
Sum of positions of an item from top(right) and bottom(left) of a list is always equal to the sum of the positions of the first and last items. So total items is = 15 + 17 - 1 = 31.