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Finding the Fourth Proportional to 781.38, 1,171.67 and 261.20

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Solution

The fourth proportional to 781.38, 1,171.67 and 261.20 is: 391.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.38 : 1,171.67 = 261.20 : x
  2. Step 2: Convert to fraction form
    781.38/1,171.67 = 261.20/x
  3. Step 3: Cross multiply
    781.38x = 1,171.67 × 261.20
  4. Step 4: Simplify right side
    781.38x = 306,040.20
  5. Step 5: Solve for x
    x = 306,040.20/781.38
  6. Step 6: Final answer
    x = 391.67

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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.