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Finding the Fourth Proportional to 428.92, 643.13 and 212.49

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Solution

The fourth proportional to 428.92, 643.13 and 212.49 is: 318.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.92 : 643.13 = 212.49 : x
  2. Step 2: Convert to fraction form
    428.92/643.13 = 212.49/x
  3. Step 3: Cross multiply
    428.92x = 643.13 × 212.49
  4. Step 4: Simplify right side
    428.92x = 136,658.69
  5. Step 5: Solve for x
    x = 136,658.69/428.92
  6. Step 6: Final answer
    x = 318.61

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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.