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Finding the Fourth Proportional to 687.12, 1,031.04 and 399.12

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Solution

The fourth proportional to 687.12, 1,031.04 and 399.12 is: 598.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    687.12 : 1,031.04 = 399.12 : x
  2. Step 2: Convert to fraction form
    687.12/1,031.04 = 399.12/x
  3. Step 3: Cross multiply
    687.12x = 1,031.04 × 399.12
  4. Step 4: Simplify right side
    687.12x = 411,508.68
  5. Step 5: Solve for x
    x = 411,508.68/687.12
  6. Step 6: Final answer
    x = 598.89

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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.