# How to find missing number in A.P.?

To do: To find the missing number in an A.P.

Solution:

Let $a,$ ____, $b$ is an A.P. Let the the missing term be $x$.

As known in an A.P.

$second\ term-first\ term=third\ term-first\ term$

$\Rightarrow x-a=b-x$

$\Rightarrow x+x=a+b$

$\Rightarrow 2x=a+b$

$\Rightarrow x=\frac{a+b}{2}$

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