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Finding the Fourth Proportional to 687.78, 1,031.28 and 471.42

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Solution

The fourth proportional to 687.78, 1,031.28 and 471.42 is: 706.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    687.78 : 1,031.28 = 471.42 : x
  2. Step 2: Convert to fraction form
    687.78/1,031.28 = 471.42/x
  3. Step 3: Cross multiply
    687.78x = 1,031.28 × 471.42
  4. Step 4: Simplify right side
    687.78x = 486,166.02
  5. Step 5: Solve for x
    x = 486,166.02/687.78
  6. Step 6: Final answer
    x = 706.86

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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.