Question

In a row at a bus stop, A is 7th from the left and B is 9th from the right. They both interchange their positions. A becomes 11th from the left. How many people are there in the row?

• A. 18
• B. 19
• C. 20
• D. 21

Answer 1

The Correct Option is B

To solve this problem, we need to determine the total number of people in the row after the interchange of positions between A and B.

1. Initially, A is 7th from the left and B is 9th from the right.
2. After the interchange, A becomes 11th from the left.
3. Since positions of A and B are interchanged, B now occupies the initial position of A, which was 7th from the left, and A occupies the initial position of B, which was 9th from the right.
4. Now, since A is 11th from the left, this means that A has moved from the 7th position to the 11th, which implies the total number of people must allow for these positions to match.
5. Consider the position of B, which was initially 9th from the right and after interchange becomes 7th from the left. If B is 9th from the right and A is now 11th from the left in B's initial position, the total number of people in the row can be calculated using the relationship:
   Total people = Left position of B + Right position of A - 1.
6. Substitute the values: Left position of B = 7, Right position of A = 9
7. Therefore, Total people = 7 + 9 - 1 = 15.
8. However, we must account for the overlap when A becomes 11th from the left, suggesting a calculation error or misinterpretation. Re-evaluating: If A is 11th from the left with B's original position being 9th from the right, the equation becomes:
   Total people = Left position of new B + Right position of original B - 1
   Total people = 11 + 9 - 1 = 19.
9. This reflects the correct adaptation of their positions according to all movement accounted for, showing the total number of people in the row is 19.