To solve the problem, let’s determine the total number of people in the queue and then calculate the position of A from the back.
Step 1: Determine Total Number of People in the Queue
The position of B from the front is 15th, and the position of B from the back is 21st.
The formula to find the total number of people in a queue is:
Total People=Position from Front+Position from Back−1\text{Total People} = \text{Position from Front} + \text{Position from Back} - 1
Substitute the values for B:
Total People=15+21−1=35\text{Total People} = 15 + 21 - 1 = 35Total People=15+21−1=35
Step 2: Find A’s Position from the Back
The position of A from the front is 7th. The formula to find the position from the back is:
Position from Back=Total People−Position from Front+1\text{Position from Back} = \text{Total People} - \text{Position from Front} + 1
Substitute the values for A:
Position from Back=35−7+1=29\text{Position from Back} = 35 - 7 + 1 = 29Position from Back=35−7+1=29
Final Answer:
(3) 29th
