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Finding the Fourth Proportional to 428.72, 643 and 140.12

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Solution

The fourth proportional to 428.72, 643 and 140.12 is: 210.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.72 : 643 = 140.12 : x
  2. Step 2: Convert to fraction form
    428.72/643 = 140.12/x
  3. Step 3: Cross multiply
    428.72x = 643 × 140.12
  4. Step 4: Simplify right side
    428.72x = 90,097.16
  5. Step 5: Solve for x
    x = 90,097.16/428.72
  6. Step 6: Final answer
    x = 210.15

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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.