# algebra

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The sum of the first n counting numbers 1 + 2 + 3 + 4 + 5 ... + n is given by S = n/2(1 + n).

a) Find the sum of the numbers 14 to 40 inclusive

Answer is 729. But i don't get why.

Someone explain what the qestion means by "inclusive" please ><!

• algebra -

you want the sum of the numbers from 14 to 40 inclusive (the inclusive means that the number 40 is to be included in the count)

the formula you have given only works if we start at 1
so why not find the sum from 1 to 40, then the sum from 1 to 13 and subtract that.
Wouldn't you end up with only those from 14 to 40 added up??
Let me know what you got this time.

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