ISI 2004 PEA

[shwetasogani]

Q19 Q24 anyone???

[shwetasogani]

[Akash]

24. is derangement theorem and the number of ways = n![1-1/1!+1/2!-1/3!......(-1)^n/n!] and answer must be 9

[Akash]

Put a, ar ,ar^2 and ar^3 in place of a,b,c,d and you should get they have a common r^3. Thus G.P.