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Finding the Fourth Proportional to 439.80, 655.71 and 428.40

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Solution

The fourth proportional to 439.80, 655.71 and 428.40 is: 638.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    439.80 : 655.71 = 428.40 : x
  2. Step 2: Convert to fraction form
    439.80/655.71 = 428.40/x
  3. Step 3: Cross multiply
    439.80x = 655.71 × 428.40
  4. Step 4: Simplify right side
    439.80x = 280,906.16
  5. Step 5: Solve for x
    x = 280,906.16/439.80
  6. Step 6: Final answer
    x = 638.71

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.