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Finding the Fourth Proportional to 428.60, 642.84 and 140

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Solution

The fourth proportional to 428.60, 642.84 and 140 is: 209.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.60 : 642.84 = 140 : x
  2. Step 2: Convert to fraction form
    428.60/642.84 = 140/x
  3. Step 3: Cross multiply
    428.60x = 642.84 × 140
  4. Step 4: Simplify right side
    428.60x = 89,997.60
  5. Step 5: Solve for x
    x = 89,997.60/428.60
  6. Step 6: Final answer
    x = 209.98

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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.