Self Maths Puzzle Numerical Ability Number System

what is the next term in this series :
1,2,6,20,70,..... ?

options :
1)210
2)220
3)242
4)252
5)332
6)462
7)495
8)505
9)540
10)552

Read Solution (Total 3)

252 is the answer
(2*n)!/(n!)^2 is the logic.
9 years agoHelpfull: Yes(1) No(1)

Ans = 252

(2n)!/(n!)^2 n=0,1,2,3,4,5...............
9 years agoHelpfull: Yes(0) No(1)
( (2*n) ! / (n!)^2 )
put n=0,1,2,3,4,5
ex= put 2 = (2*2) ! / (2!)^2 = 4!/(2*1)^2 = (4*3*2*1)/ 2*2 = 6......@kash
9 years agoHelpfull: Yes(0) No(0)

Self Other Question

6 coins are tossed What is the probability of getting 3 heads and 3 tails (HHHTTT) ? There are N doors in a row numbered from 1 to N. Initially all are closed.
Then you make N passes by the N doors. In pass 1 you toggle the all the doors starting from the first door. In the second pass you toggle every second door. In the third pass you toggle all third doors.Similarly you make N passes.Question is what is the state of door k after N passes.