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Finding the Fourth Proportional to 640.38, 961.02 and 421

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Solution

The fourth proportional to 640.38, 961.02 and 421 is: 631.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    640.38 : 961.02 = 421 : x
  2. Step 2: Convert to fraction form
    640.38/961.02 = 421/x
  3. Step 3: Cross multiply
    640.38x = 961.02 × 421
  4. Step 4: Simplify right side
    640.38x = 404,589.42
  5. Step 5: Solve for x
    x = 404,589.42/640.38
  6. Step 6: Final answer
    x = 631.80

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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.