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Finding the Fourth Proportional to 428.15, 642.43 and 197.20

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Solution

The fourth proportional to 428.15, 642.43 and 197.20 is: 295.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.15 : 642.43 = 197.20 : x
  2. Step 2: Convert to fraction form
    428.15/642.43 = 197.20/x
  3. Step 3: Cross multiply
    428.15x = 642.43 × 197.20
  4. Step 4: Simplify right side
    428.15x = 126,688.25
  5. Step 5: Solve for x
    x = 126,688.25/428.15
  6. Step 6: Final answer
    x = 295.90

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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.