1) the two sequences of numbers {1,4,16,64,.............} and{3,12,48,192,....................} are mixed as {1,3,4,12,16,48,64,192,.......}.If one number in the mixed series is 1048576 then its just preceeding number is.(A)262144 (B)786432 (C)3245728 (D) NOT POSSIBLE TO FIND IT

It can be seen that the first sequence is 4^n-1 where n=1,2,3,.... Second sequence is 3*4^n-1 where n=1,2,3,..... 1048576=4^10. So this is the 11th term of the first series. The preceeding term will be the 10th term of the second series. So substitute n=10 in the second series, we get 3*4^9 which will evidently be option B.