Find the average of the first fifteen multiples of 11.

Sum of AP = \(\frac{n}{2}\) (2a + (n-1)d)

Sum of 1st fifteen multiples of 11 = \(\frac{d15}{2}\) (2 x 11 + 14 x 11)

                                                = 1320

Average of 1st fifteen multiples of 11 = \(\frac{1320}{15}\)

                                                      = 88