First-term and the common differences of an A.P. are 6 and 3 respectively; find S27.
**Solution:**
First term = a = 6 , common difference = d = 3, S27 = ?
Sn = \[\frac n2 [\Box + (n-1) d ]\]
S27= $27/2$ [12 + (27 - 1)\[\Box ]\]
=$27/2$ \[\Box\]
=27 45 = \[\Box \]
