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Finding the Fourth Proportional to 691.38, 1,039.23 and 639.54

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Solution

The fourth proportional to 691.38, 1,039.23 and 639.54 is: 961.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    691.38 : 1,039.23 = 639.54 : x
  2. Step 2: Convert to fraction form
    691.38/1,039.23 = 639.54/x
  3. Step 3: Cross multiply
    691.38x = 1,039.23 × 639.54
  4. Step 4: Simplify right side
    691.38x = 664,629.15
  5. Step 5: Solve for x
    x = 664,629.15/691.38
  6. Step 6: Final answer
    x = 961.31

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.