The first term of a H P whose second term is 52 and third term is 103, is___
Let x be the first term of H.P.
x, 52, 103 are in H.P.
⇒ 1x, 25, 310 are in A.P.
So, 25 - 1x = 310 - 25
- 1x = 310 - 45
1x = 12
x = 2
So, the first term = 2
Find the sum of first 20 terms of an A. P. whose first term is 3 and the last term is 57.