Question

How many terms of the arithmetic sequence 2 4 6 8 will give a sum of 600?

Answer 1

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a = 2

d = 4 - 2 = 2

Sn = 600

Now,

$Sn \: = \: \frac{n}{2} (2a \: + \: (n - 1)d)$

=> 600 = n/2 ( 2(2) + (n-1)(2))

=> 1200 = n [4 + 2n - 2]

=> 1200 = 2n + 2n²

=> n² + n - 600 = 0

Now,

n = 24 ; -25

So,

The sum of 24 digits of the AP 2,4,6....... is 600.

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