Question

find the sum of the following AP 34 ,32 ,30........20​

Answer 1

AP : 34 + 32 + 30......+10

First term (a): 34

Last term (l): 10

l = a + (n-1)d

10 = 34 + (n-1) (-2)

Total no. Of terms n = 13

Sum = n(a+l)/2

=13(34+10)/2

=286

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Answer 2

Answer:

216.

Step-by-step explanation:

Given:-

a = 34 , d = - 2 , l = 10

We know that,

Sn = n/2 ( a + l)

We have to find out n =?..

An = a + ( n - 1) d

20 = 34 + ( n- 1) (- 2)

20 = 34 - 2n + 2

20 = 36 - 2n

- 16 = - 2n

n = 8.

S8 = 8/2 ( 34 + 20)

S8 = 8/2 x 54

S8 = 4 x 54

S8 = 216.

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