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Finding the Fourth Proportional to 431.67, 647.44 and 139.20

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Solution

The fourth proportional to 431.67, 647.44 and 139.20 is: 208.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    431.67 : 647.44 = 139.20 : x
  2. Step 2: Convert to fraction form
    431.67/647.44 = 139.20/x
  3. Step 3: Cross multiply
    431.67x = 647.44 × 139.20
  4. Step 4: Simplify right side
    431.67x = 90,122.57
  5. Step 5: Solve for x
    x = 90,122.57/431.67
  6. Step 6: Final answer
    x = 208.78

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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.