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Finding the Fourth Proportional to 781.39, 1,171.69 and 261.21

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Solution

The fourth proportional to 781.39, 1,171.69 and 261.21 is: 391.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.39 : 1,171.69 = 261.21 : x
  2. Step 2: Convert to fraction form
    781.39/1,171.69 = 261.21/x
  3. Step 3: Cross multiply
    781.39x = 1,171.69 × 261.21
  4. Step 4: Simplify right side
    781.39x = 306,057.14
  5. Step 5: Solve for x
    x = 306,057.14/781.39
  6. Step 6: Final answer
    x = 391.68

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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.