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Finding the Fourth Proportional to 687.70, 1,031.60 and 413.20

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Solution

The fourth proportional to 687.70, 1,031.60 and 413.20 is: 619.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    687.70 : 1,031.60 = 413.20 : x
  2. Step 2: Convert to fraction form
    687.70/1,031.60 = 413.20/x
  3. Step 3: Cross multiply
    687.70x = 1,031.60 × 413.20
  4. Step 4: Simplify right side
    687.70x = 426,257.12
  5. Step 5: Solve for x
    x = 426,257.12/687.70
  6. Step 6: Final answer
    x = 619.83

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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.