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Difficulty: 2/102024 NMTC 2024 (QII-62)

Determine the sum of the geometric series: 4 + 2 + 1 + 1/2 + .

Guide / Hint

Hint 1: Identify that this is an infinite geometric series.

Hint 2: Find the first term and the common ratio .

Hint 3: Use the sum formula to calculate the final sum.

Solution

Step 1 (Identify Series Type): The given series is . This is an infinite geometric series where:

  • The first term is

  • The common ratio is

Step 2 (Verify Convergence): The common ratio satisfies , which means the infinite geometric series converges to a finite sum.

Step 3 (Apply Sum Formula): The sum of an infinite geometric series is given by:

Step 4 (Conclusion): The sum of the geometric series is exactly 8.

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