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Finding the Fourth Proportional to 812.86, 1,217.91 and 640.64

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Solution

The fourth proportional to 812.86, 1,217.91 and 640.64 is: 959.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    812.86 : 1,217.91 = 640.64 : x
  2. Step 2: Convert to fraction form
    812.86/1,217.91 = 640.64/x
  3. Step 3: Cross multiply
    812.86x = 1,217.91 × 640.64
  4. Step 4: Simplify right side
    812.86x = 780,241.86
  5. Step 5: Solve for x
    x = 780,241.86/812.86
  6. Step 6: Final answer
    x = 959.88

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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.