AP ICET 2017 Shift 2 Paper

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Question : 128 of 200

Marks: +1, -0

If

a_{1},a_{2},a_{3},............,a_{19}

are 19 arithmetic means between

1/4

and

-39/4

then

a_7=

$-11/4$
$-13/4$
$-15/4$
$-17/4$

Solution:

Since there are 19 arithmetic means between

1/4

and

{-39}/4

⇒{1}/{4}+(21-1)d={-39}/{4}

⇒20d={-40}/{4}⇒d=-{1}/{2}

∴a_{7}={1}/{4}+7(-{1}/{2})={1}/{4}-{14}/{4}={-13}/{4}

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