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Finding the Fourth Proportional to 428.19, 642.30 and 211.69

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Solution

The fourth proportional to 428.19, 642.30 and 211.69 is: 317.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.19 : 642.30 = 211.69 : x
  2. Step 2: Convert to fraction form
    428.19/642.30 = 211.69/x
  3. Step 3: Cross multiply
    428.19x = 642.30 × 211.69
  4. Step 4: Simplify right side
    428.19x = 135,968.49
  5. Step 5: Solve for x
    x = 135,968.49/428.19
  6. Step 6: Final answer
    x = 317.54

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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.