What you have are describing is (the sum of digits from 1 to N) * 200.

The equation for the sum of the digits is (N+1)*N/2.

The logic is very clever. Create pairs by selecting 2 numbers from the
original N values, but don't do it at random: do it by pairing 1 with N, 2
with N - 1, 3 with N - 2, etc.

Note that the sum of each pair is N + 1 (e.g. 5 + N - 4 = N + 1)

So, if you know how many pairs there are, the total is (N+1) * number of
pairs. The number of pairs = N/2.

So the sum of the digits from 1 through N, inclusive is (N+1)*N/2

If you put N in cell C1, the formula for A1 is

=200*C1/2*(1+C1)


On Wed, 27 Oct 2004 19:38:04 -0500, kidd
wrote:


I am trying to make a formula that adds the amount at 200 and then the
amount if it double and triples without a limit.

Example: 1=200 /2 = 200+400/ 3 = 200+400+600/ 4 = 200+400+600+800 / 5
= 200+400+600+800+1000/ 6 = 200+400+600+800+1000+1200

If they enter in A1 the number 4

then in C1 then answer should be 2000

If they enter in A1 the number 6
then in C1 the answer should be 4200

Can anyone HELP ME PLEASE