Question

What is the common difference of an ap in which a 21st term and the 7th term difference is 84?

Answer 1

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Answer 2

The common difference of an ap is 6

Step-by-step explanation:

Formula of nth term of AP = $a_n=a+(n-1)d$

Where a is the first term

n is the term number

d is the common difference

Substitute n= 21

So,$a_{21}=a+(21-1)d$

Substitute n = 7

So, $a_7=a+(7-1)d$

We are given that the common difference of an ap in which a 21st term and the 7th term difference is 84

So, $a+(21-1)d-(a+(7-1)d)=84\\a+20d-a-6d=84\\14d=84\\d=6$

Hence The common difference of an ap is 6

#Learn more :

If an AP the common difference and 7th term is 4 then find the first term

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