03-24-2011, 10:08 AM
I am not good at sequences, but i tried. 65/2= 32.5, the second number is 2.5 more than 32.5(ie. 35). 35/2= 17.5, the third number is 0.5 less than 17.5(ie 17). So the sequence is a, b=a/2+2.5, c=b/2-0.5, d=c/2+2.5, e=d/2-0.5 and so on. Therefore the fourth number is 17/2+2.5= 11.