Question

The arithmetic sequence a; is defined by the formula:

a1=4

ai = ai-1 + 11

Find the sum of the first 650 terms in the sequence.

Answer 1

The sum of the first 650 terms of the given arithmetic sequence is 2,322,775

Explanation:

The first term here is 4

while the nth term would be ai = a(i-1) + 11

Kindly note that i and 1 are subscript of a

Mathematically, the sum of n terms of an arithmetic sequence can be calculated using the formula

Sn = n/2[2a + (n-1)d)

Here, our n is 650, a is 4, d is the difference between two successive terms which is 11.

Plugging these values, we have

Sn = (650/2) (2(4) + (650-1)11)

Sn = 325(8 + 7,139)

Sn = 325(7,147)

Sn = 2,322,775