Worked problem · Calculus II · Unit 4A

Repeating Decimal As A Series: Worked Example and Solution

A complete geometric-series structure example with method choice, derivation, verification, and a common wrong approach.

1 problem8 min estimated timeFoundational to intermediate progression

Problem

  1. Write 0.272727… as a fraction.

Complete worked solutions

Every problem has a source-matched answer and independently reviewed derivation.

01

Problem 1: Write 0.272727… as a fraction.

Answer: 3/113/11

Why this method: Geometric-series structure matches the mathematical structure before any algebraic cleanup.

  1. Write the decimal as 27/100+27/10000+27/100+27/10000+\cdots.
  2. This has a=27/100a=27/100, r=1/100r=1/100, so its sum is 27/99=3/1127/99=3/11.
  3. Therefore the result is 3/113/11.

What is included

See a concise answer and full derivation for write 0.272727… as a fraction.

Skills assessed

  • Geometric-series structure

Prerequisites

  • sequences
  • sigma notation
Repeating Decimal As A Series instructional sequence
A complete geometric-series structure example with method choice, derivation, verification, and a common wrong approach. The numbered labels and written sequence preserve meaning without relying on color.
Long description

Read the diagram from top to bottom. Each numbered box names one decision or mathematical operation. Arrows show the required order; the text labels remain the complete interpretation in print, dark mode, and nonvisual reading.

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Common errors

  • Using the infinite-sum formula without checking the common-ratio condition or the starting index.