Question

In how many ways can 6 letters a, b, c, d, e and f be arranged in a row such that d is always somewhere between a and b?

Answer 1

As d is always between a and b, positon of d is fixed that is it always come before b.

there are 5 ways for A to take positon in a row as it can't take position at last

there are 4 ways for B and D to take position in a row as there position is fixed

there are 4 ways for C to take position in a row and 3 way for E and 2 for F.

No of ways of arrangement of all the letters=

5*4*4*3*2/2 = 240

Answer = 240