In our last discussion, we had the following formula:

Sum of a series of numbers = 1/2 of [ N x (F + L) ]

We used it to find the sum of consecutive numbers.

Suppose, we have the following series:

1, 3, 5, 7, 9, 11, 13, 15, 17, 19

Is our formula applicable? We have ten numbers (N = 10). First number in the series is 1 (F = 1) and the last number is 19 (L = 19).

Using our formula we now have:

Sum of the series = 1/2 of [ 10 x (1 + 19) ]

Sum of the series = 1/2 x [200]

Sum of the series = 100 which is the correct answer.

The same formula applies not only to a series of consecutive numbers but also to other math series with constant difference such as 1, 3, 5, 7, 9, 11, 13, 15, 17, 19.

## Tuesday, August 14, 2007

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