Question

The 4 and 8 term of an A.P. are in the ratio 1:2 and
the 10th term is 30. Find the common difference and
the first term. Write the A.P.
​

Answer 1

4th and 8th term of an AP is in ratio 1:2.

That is,  

a4:a8 = 1:2

So,

a+3d/a+7d = 1/2

2(a+3d) = (a+7d)

2a+6d=a+7d

a=d