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Find 1 + 3 + 5 + 7 + ... + 99.

 Jun 22, 2020
 #1
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This thing (the problem lol) is an arithmetic progression.

there's a formula for this type of problem.

 

Let's say A is the first term and An is the last term, and d is how much each number is increasing from the last. so first we should first find the number of terms in the progression. the equation is:

 

An = a+(n-1)d

 

so ya plug in the values:

 

99=1+(n-1)2

98=(n-1)2

n-1=49

And n=50

There are 50 terms in all…

 

Now the sum of these fifty terms:

 

Sn = n/2(A+An)

S50=25(1+99)

Sooooo the answer is 25*100 = 2500

 Jun 22, 2020

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