Find tn of the A.P. : 3, 6 , 9, .......

Here, a = 3, d = 6 – 3 = 3

We know that,

tn = a + (n – 1) d

∴ tn  = 3 + (n – 1) 3

∴ tn = 3 + 3n – 3

∴ tn = 3n