Question

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How many terms of the A.P. 27, 24, 21, … should be taken so that their sum is zero?



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Answer 1

QuestioN :

How many terms of the A.P. 27, 24, 21, … should be taken so that their sum is zero?

SolutioN :

"Your answer is in the given attachment."

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Answer 2

The correct option is A

19

Given that AP is 27, 24, 21 …

a = 27 ; d = 24 - 27 = (-3)

Sn=n2(2a+(n−1)d)

Since the sum is 0,

⇒n2(2×27+(n−1)(−3))=0

⇒n(54−3n+3)=0

⇒n(57−3n)=0

⇒n=0 and 57−3n=0

⇒57=3n

∴n=0 and n=19

Since the number of terms cannot be equal to 0, so n = 19

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