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Finding the Fourth Proportional to 688.70, 1,031.69 and 428.09

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Solution

The fourth proportional to 688.70, 1,031.69 and 428.09 is: 641.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    688.70 : 1,031.69 = 428.09 : x
  2. Step 2: Convert to fraction form
    688.70/1,031.69 = 428.09/x
  3. Step 3: Cross multiply
    688.70x = 1,031.69 × 428.09
  4. Step 4: Simplify right side
    688.70x = 441,648.87
  5. Step 5: Solve for x
    x = 441,648.87/688.70
  6. Step 6: Final answer
    x = 641.28

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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.