Question

The sum of first 6 termsof an A.P is 42.The ratio of its 10th tern to its 30th termis 1:3.Calculate the first and 13th term of the A.P.

Answer 1

Answer:

s5=5/2*(2a+4d)

42=5a+10d........(I)

....(a+9d)/(a+29d) =1/3

3a+27d=a+29d

a-d=0..........(2)

eliminate.....

hence it will be a=d=42/15

so first term is 42/15

and hence thirteenth term will be 546/15