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Finding the Fourth Proportional to 781.90, 1,172.87 and 261.91

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Solution

The fourth proportional to 781.90, 1,172.87 and 261.91 is: 392.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    781.90 : 1,172.87 = 261.91 : x
  2. Step 2: Convert to fraction form
    781.90/1,172.87 = 261.91/x
  3. Step 3: Cross multiply
    781.90x = 1,172.87 × 261.91
  4. Step 4: Simplify right side
    781.90x = 307,186.38
  5. Step 5: Solve for x
    x = 307,186.38/781.90
  6. Step 6: Final answer
    x = 392.87

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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.