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Finding the Fourth Proportional to 521.19, 781.31 and 405

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Solution

The fourth proportional to 521.19, 781.31 and 405 is: 607.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    521.19 : 781.31 = 405 : x
  2. Step 2: Convert to fraction form
    521.19/781.31 = 405/x
  3. Step 3: Cross multiply
    521.19x = 781.31 × 405
  4. Step 4: Simplify right side
    521.19x = 316,431.56
  5. Step 5: Solve for x
    x = 316,431.56/521.19
  6. Step 6: Final answer
    x = 607.13

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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.