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Finding the Fourth Proportional to 428.76, 643.12 and 140.20

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Solution

The fourth proportional to 428.76, 643.12 and 140.20 is: 210.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.76 : 643.12 = 140.20 : x
  2. Step 2: Convert to fraction form
    428.76/643.12 = 140.20/x
  3. Step 3: Cross multiply
    428.76x = 643.12 × 140.20
  4. Step 4: Simplify right side
    428.76x = 90,165.42
  5. Step 5: Solve for x
    x = 90,165.42/428.76
  6. Step 6: Final answer
    x = 210.29

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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.