Sum of the first 20 terms of an AP is -240, and its first term is 7. Find its 24th term.

Given : Sum of 20 terms of an AP = -240 and First term 7
Sum of first n terms of an AP is given as S = n/2[2a + (n-1)d]
n = 20, S = -240, a = 7
⇒ -240 = 20/2[2 × 7 + (20 - 1)d]
⇒ -240 = 10[14 + 19d]
⇒ -240 = 140 + 190d
⇒ -190d = 140 + 240
⇒ -190d = 380
⇒ d = 380 / -190 = -2
nth term of an AP = an = a + (n - 1)d
⇒ a24 = 7 + (24 - 1)(-2)
⇒ a24 = 7 - 46
⇒ a24 = -39