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Finding the Fourth Proportional to 781.20, 1,171.91 and 261.03

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Solution

The fourth proportional to 781.20, 1,171.91 and 261.03 is: 391.58

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.20 : 1,171.91 = 261.03 : x
  2. Step 2: Convert to fraction form
    781.20/1,171.91 = 261.03/x
  3. Step 3: Cross multiply
    781.20x = 1,171.91 × 261.03
  4. Step 4: Simplify right side
    781.20x = 305,903.67
  5. Step 5: Solve for x
    x = 305,903.67/781.20
  6. Step 6: Final answer
    x = 391.58

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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.