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Finding the Fourth Proportional to 399.12, 550.44 and 311.64

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Solution

The fourth proportional to 399.12, 550.44 and 311.64 is: 429.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    399.12 : 550.44 = 311.64 : x
  2. Step 2: Convert to fraction form
    399.12/550.44 = 311.64/x
  3. Step 3: Cross multiply
    399.12x = 550.44 × 311.64
  4. Step 4: Simplify right side
    399.12x = 171,539.12
  5. Step 5: Solve for x
    x = 171,539.12/399.12
  6. Step 6: Final answer
    x = 429.79

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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.