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Finding the Fourth Proportional to 687.78, 1,031.31 and 379.53

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Solution

The fourth proportional to 687.78, 1,031.31 and 379.53 is: 569.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    687.78 : 1,031.31 = 379.53 : x
  2. Step 2: Convert to fraction form
    687.78/1,031.31 = 379.53/x
  3. Step 3: Cross multiply
    687.78x = 1,031.31 × 379.53
  4. Step 4: Simplify right side
    687.78x = 391,413.08
  5. Step 5: Solve for x
    x = 391,413.08/687.78
  6. Step 6: Final answer
    x = 569.10

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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.