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Finding the Fourth Proportional to 421.28, 628.78 and 387.08

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Solution

The fourth proportional to 421.28, 628.78 and 387.08 is: 577.73

Step by Step Solution

  1. Step 1: Write the proportion equation
    421.28 : 628.78 = 387.08 : x
  2. Step 2: Convert to fraction form
    421.28/628.78 = 387.08/x
  3. Step 3: Cross multiply
    421.28x = 628.78 × 387.08
  4. Step 4: Simplify right side
    421.28x = 243,388.16
  5. Step 5: Solve for x
    x = 243,388.16/421.28
  6. Step 6: Final answer
    x = 577.73

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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.