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Finding the Fourth Proportional to 428.07, 642.11 and 211.80

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Solution

The fourth proportional to 428.07, 642.11 and 211.80 is: 317.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.07 : 642.11 = 211.80 : x
  2. Step 2: Convert to fraction form
    428.07/642.11 = 211.80/x
  3. Step 3: Cross multiply
    428.07x = 642.11 × 211.80
  4. Step 4: Simplify right side
    428.07x = 135,997.84
  5. Step 5: Solve for x
    x = 135,997.84/428.07
  6. Step 6: Final answer
    x = 317.70

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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.