Latest CAT Aptitude Question SOLUTION: The sum of the first and the 9th term of an arithmetic progression is 24. What is the sum of the first nine terms of the progression?

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The sum of the first and the 9th term of an arithmetic progression is 24. What is the sum of the first nine terms of the progression?

Asked In CAT Devendra Marghade (12 years ago)

Solved Mahesh Read Solution (3)

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Read Solution (3) :

Vignesh  (12 years ago)

Sum of the first nine terms of the progression is 108.

** Sum of first 'n' terms of an A.P is = n/2(first term + last term)
where
n = number of terms

** Sum of the first 9 terms is = 9/2(first term + last term)

** Sum of the first 9 terms is = 9/2(24) ==> 108
where
first term + last term = 24

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Mahesh  (12 years ago)

sum of the first nine terms of the progression 24*9/2 = 108

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teza  (11 years ago)

The sum S of the first n values of a finite sequence is given by the formula:

S = 1/2(a1 + an)n, where a1 is the first term and an the last.
given a1+an=24;
so,1/2(24)*9=108;

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