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Finding the Fourth Proportional to 428.91, 643.89 and 407.39

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Solution

The fourth proportional to 428.91, 643.89 and 407.39 is: 611.58

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.91 : 643.89 = 407.39 : x
  2. Step 2: Convert to fraction form
    428.91/643.89 = 407.39/x
  3. Step 3: Cross multiply
    428.91x = 643.89 × 407.39
  4. Step 4: Simplify right side
    428.91x = 262,311.13
  5. Step 5: Solve for x
    x = 262,311.13/428.91
  6. Step 6: Final answer
    x = 611.58

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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.