3 answers:

HarryC said...

315

The differences between the numbers are: 2240, 3360, 2520, and 210. That doesn't follow any discernable pattern, unless you look at the ratio of the differences to the original number:

2240 / 8960 = .25
3360 / 6720 = .5
2520 / 3360 = .75
210 / 840 = .25

So, we have a repeating sequence in the ratios { .25, .5, .75 }. The next in the sequence is .5, , meaning the next number will be half the current number, hence 315.

10/30/2009 1:39 PM

sadeesh said...

8960 * 0.75 = 6720
6720 * 0.5 = 3360
3360 * 0.25 = 840
again...
840 * 0.75 = 630
630 * 0.5 = 315
315 * 0.25 = 78.75 ......

so the seq would be
8960, 3360, 840, 630, 315, 78.75, ......

11/02/2009 12:15 AM

Mike said...

As always, you impress me with how you get these. The answer, as already pointed out by harryc and sadeesh is 315.

11/02/2009 9:26 AM