Question

OR
The sum of first, third and the fifth term of an A.P is 21. The sum of second, fourth
and sixth term of the same A.P is 30. Find the sum to 20 terms of that A.P.​

Answer 1

Answer:

Let the three terms of A.P are a,a+d,a+2d.

Now,As per the question ,

a+a+d+a+2d=3a+3d=21

i.e. a+d=7 or, d=7−a.

Now,a(a+2d)−(a+d)=6

a{a+2(7−a)}−7=6

a{a+14−2a}=13

a{14−a}=13

14a−a

2

=13

a

2

−14a+13=0

By factorising,we get

a=13,1

d=7−a

For a=13,1d=7−13,7−1=−6,6 respectively.

Now, there are two AP's a,a+d,a+2d for two values of a and d

13,7,1 and 1,7,13

Answer 2

ans is 0

hope this helps you