Choose the correct answer from the given four options:
In an $ \mathrm{AP} $, if $ d=-4, n=7, a_{n}=4 $, then $ a $ is
(A) 6
(B) 7
(C) 20
(D) 28

AcademicMathematicsNCERTClass 10

Given: 

In an A.P., $d = –4,\ n = 7,\ a_n=4$.

To do: 

We have to find the value $a$.

Solution:

We know that,

$n^{th}$ term of A.P. $a_n=a+( n-1)d$

On substituting the values,

$\Rightarrow 4=a+( 7-1)( -4)$

$\Rightarrow 4=a-24$

$\Rightarrow a=24+4$

$\Rightarrow a=28$

Hence, $a=28$. 

raja
Updated on 10-Oct-2022 13:27:27

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