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Finding the Fourth Proportional to 781.35, 1,171.80 and 287.70

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Solution

The fourth proportional to 781.35, 1,171.80 and 287.70 is: 431.47

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.35 : 1,171.80 = 287.70 : x
  2. Step 2: Convert to fraction form
    781.35/1,171.80 = 287.70/x
  3. Step 3: Cross multiply
    781.35x = 1,171.80 × 287.70
  4. Step 4: Simplify right side
    781.35x = 337,126.86
  5. Step 5: Solve for x
    x = 337,126.86/781.35
  6. Step 6: Final answer
    x = 431.47

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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.