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Finding the Fourth Proportional to 687.78, 949.20 and 393.11

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Solution

The fourth proportional to 687.78, 949.20 and 393.11 is: 542.52

Step by Step Solution

  1. Step 1: Write the proportion equation
    687.78 : 949.20 = 393.11 : x
  2. Step 2: Convert to fraction form
    687.78/949.20 = 393.11/x
  3. Step 3: Cross multiply
    687.78x = 949.20 × 393.11
  4. Step 4: Simplify right side
    687.78x = 373,135.27
  5. Step 5: Solve for x
    x = 373,135.27/687.78
  6. Step 6: Final answer
    x = 542.52

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.