Question

The first term of an A.P. is-3&
tenth term is 24. Find the 20th term​

Answer 1

Answer:

Step-by-step explanation:

Given ,  

First term =a=12

Let the common difference be d

and we know 7th term a  

7

​  

=a+6d

and 11th term a  

11

​  

=a+10d  

According to question ,

                  a  

11

​  

−a  

7

​  

=24

a+10d−(a+6d)=24

   a+10d−a−6d=24

                             4d=24

                              d=6

We know that,  

20th term =a  

20

​  

=a+19d=12+19(6)=12+114=126

So , the 20th term of AP is 126

Answer 2

Answer:

First term =a=12

Let the common difference be d

and we know 7th term a  

7

​  

=a+6d

and 11th term a  

11

​  

=a+10d  

According to question ,

                  a  

11

​  

−a  

7

​  

=24

a+10d−(a+6d)=24

   a+10d−a−6d=24

                             4d=24

                              d=6

We know that,  

20th term =a  

20

​  

=a+19d=12+19(6)=12+114=126

So , the 20th term of AP is 126.

Step-by-step explanation:

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