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Finding the Fourth Proportional to 781.47, 1,171.80 and 261.28

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Solution

The fourth proportional to 781.47, 1,171.80 and 261.28 is: 391.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.47 : 1,171.80 = 261.28 : x
  2. Step 2: Convert to fraction form
    781.47/1,171.80 = 261.28/x
  3. Step 3: Cross multiply
    781.47x = 1,171.80 × 261.28
  4. Step 4: Simplify right side
    781.47x = 306,167.90
  5. Step 5: Solve for x
    x = 306,167.90/781.47
  6. Step 6: Final answer
    x = 391.78

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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.