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Finding the Third Proportional to 978 and 1,089

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Solution

The third proportional to 978 and 1,089 is: 1,212.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    978 : 1,089 = 1,089 : x
  2. Step 2: Convert to fraction form
    978/1,089 = 1,089/x
  3. Step 3: Cross multiply
    978x = 1,089 × 1,089
  4. Step 4: Simplify right side
    978x = 1,185,921
  5. Step 5: Solve for x
    x = 1,185,921/978
  6. Step 6: Final answer
    x = 1,212.60

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Why These Related Problems?

These problems maintain the same ratio (1.11) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.