Discussion

Explanation:

The given numbers will form an Arithmetic Series i.e., 12 + 15 + 18 + ……. 198 and 

the number of terms is = $\frac{{\mathrm{T}}_{\mathrm{n}}-{\mathrm{T}}_1}{\mathrm{d}}$ + 1 = $\frac{198-12}{3}$ + 1 = 63

Now sum = average × number of terms = $\frac{12+198}{2}$ × 63 = 6615

Hence, option (c).

» Your doubt will be displayed only after approval.