Four persons P, Q, R and S are to be seated in a row. R should not be seated at the second position from the left end of the row. The number of distinct seating arrangements possible is:
A. 6 B. 9 C. 18 D. 24
GATE 2021 · General Aptitude · Seating Arrangement · medium
Answer: 18 distinct seating arrangements (Option C)
Total unrestricted arrangements: 4 distinct people in 4 seats: 4! = 4 * 3 * 2 * 1 = 24.
Count arrangements where R is at seat 2 (forbidden cases): Fix R at seat 2. Remaining 3 people P, Q, S fill seats 1, 3, 4 freely: 3! = 6 ways.