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.