Find the sum of each of the following APs:

– 37, – 33, – 29, ... to 12 terms.

Here, first term = - 37

Common difference = (-33) - (-37) = 4

Sum of first n terms of an AP is

S_n = [2a + (n - 1)d]

∴ S₁₂ = [2(-37) + (12 - 1)(4)]

= (6)(-74 + 44)

= 6 × (-30)

= - 180

Thus, sum of 12 terms of this AP is - 180.