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Finding the Fourth Proportional to 428.10, 642.34 and 211.64

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Solution

The fourth proportional to 428.10, 642.34 and 211.64 is: 317.55

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.10 : 642.34 = 211.64 : x
  2. Step 2: Convert to fraction form
    428.10/642.34 = 211.64/x
  3. Step 3: Cross multiply
    428.10x = 642.34 × 211.64
  4. Step 4: Simplify right side
    428.10x = 135,944.84
  5. Step 5: Solve for x
    x = 135,944.84/428.10
  6. Step 6: Final answer
    x = 317.55

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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.