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What is the sum of the series?

 Mar 19, 2019
 #1
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+2

First term =  3(1)  = 3

Last term = 3(5) = 15

 

Sum = 

 

[  first term + last term ] *  number of terms / 2  =

 

[ 3 + 15  ] *  5 / 2  =

 

18 * 5  / 2  =

 

90 / 2   =

 

45

 

cool cool cool

 Mar 19, 2019

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