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Finding the Fourth Proportional to 431.38, 646.89 and 138.79

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Solution

The fourth proportional to 431.38, 646.89 and 138.79 is: 208.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    431.38 : 646.89 = 138.79 : x
  2. Step 2: Convert to fraction form
    431.38/646.89 = 138.79/x
  3. Step 3: Cross multiply
    431.38x = 646.89 × 138.79
  4. Step 4: Simplify right side
    431.38x = 89,781.86
  5. Step 5: Solve for x
    x = 89,781.86/431.38
  6. Step 6: Final answer
    x = 208.13

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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.