Q5 of 202 Page 9

How many terms of the A.P. must be taken so that their sum is 693?

Sn = [2a + (n – 1) d]

693 = [2(63) + (n – 1) (-3)]


693 = [126 -3n + 3]


462 = n [43 – n]


n2 – 43n + 462 = 0


n = 22 or n = 21


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