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Find the sums given below : –5 + (–8) + (–11) + . . . + (–230) - Mathematics

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Find the sums given below :

–5 + (–8) + (–11) + . . . + (–230)

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Solution

−5) + (−8) + (−11) + ………… + (−230)

For this A.P.,

a = −5

l = −230

d = a2 − a1 = (−8) − (−5)

= − 8 + 5 = −3

Let −230 be the nth term of this A.P.

l = a + (n − 1)d

−230 = − 5 + (n − 1) (−3)

−225 = (n − 1) (−3)

(n − 1) = 75

n = 76

And `S_n = n/2(a+1)`

= `76/2[(-5)+(-230)`

= 38(-235)

=-8930

Concept: Sum of First n Terms of an AP
  Is there an error in this question or solution?

APPEARS IN

NCERT Class 10 Maths
Chapter 5 Arithmetic Progressions
Exercise 5.3 | Q 2.3 | Page 112
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