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Finding the Fourth Proportional to 428.32, 639.41 and 399.88

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Solution

The fourth proportional to 428.32, 639.41 and 399.88 is: 596.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.32 : 639.41 = 399.88 : x
  2. Step 2: Convert to fraction form
    428.32/639.41 = 399.88/x
  3. Step 3: Cross multiply
    428.32x = 639.41 × 399.88
  4. Step 4: Simplify right side
    428.32x = 255,687.27
  5. Step 5: Solve for x
    x = 255,687.27/428.32
  6. Step 6: Final answer
    x = 596.95

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.