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A geometric sequence has first term 5 and common ratio 2. the sum of the first n terms of the sequence is 163 835. What is n ? [Answer format: integer, no units]

2 Answers

4 votes

Final answer:

To determine the number of terms (n) in a geometric sequence that sums up to 163,835, with a first term of 5 and common ratio of 2, one must apply the sum formula for geometric series and solve for n, which yields an answer of n = 15.

Step-by-step explanation:

To find the value of n for the geometric series with a first term of 5 and a common ratio of 2 that sums to 163,835, we can use the formula for the sum of the first n terms of a geometric sequence:

Sₙ = a(1 - rn) / (1 - r), where Sn is the sum of the first n terms, a is the first term, and r is the common ratio.

Plugging our values into the formula we get:

163,835 = 5(1 - 2n) / (1 - 2).

Since the common ratio is 2, this simplifies to:

163,835 = 5(2n - 1).

Dividing both sides by 5, we have:

32,767 = 2n - 1.

Adding 1 to both sides:

32,768 = 2n, which is 2 to the power of 15.

Therefore, n equals 15.

User Micah Montoya
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4 votes

Answer:

n = 15

Step-by-step explanation:

User ColonD
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8.3k points