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Finding the Fourth Proportional to 399.13, 550.40 and 311.65

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Solution

The fourth proportional to 399.13, 550.40 and 311.65 is: 429.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    399.13 : 550.40 = 311.65 : x
  2. Step 2: Convert to fraction form
    399.13/550.40 = 311.65/x
  3. Step 3: Cross multiply
    399.13x = 550.40 × 311.65
  4. Step 4: Simplify right side
    399.13x = 171,529.23
  5. Step 5: Solve for x
    x = 171,529.23/399.13
  6. Step 6: Final answer
    x = 429.76

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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.