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Finding the Fourth Proportional to 431.21, 646.85 and 138.73

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Solution

The fourth proportional to 431.21, 646.85 and 138.73 is: 208.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    431.21 : 646.85 = 138.73 : x
  2. Step 2: Convert to fraction form
    431.21/646.85 = 138.73/x
  3. Step 3: Cross multiply
    431.21x = 646.85 × 138.73
  4. Step 4: Simplify right side
    431.21x = 89,737.50
  5. Step 5: Solve for x
    x = 89,737.50/431.21
  6. Step 6: Final answer
    x = 208.11

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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.