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Finding the Fourth Proportional to 428.89, 643.42 and 140.53

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Solution

The fourth proportional to 428.89, 643.42 and 140.53 is: 210.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.89 : 643.42 = 140.53 : x
  2. Step 2: Convert to fraction form
    428.89/643.42 = 140.53/x
  3. Step 3: Cross multiply
    428.89x = 643.42 × 140.53
  4. Step 4: Simplify right side
    428.89x = 90,419.11
  5. Step 5: Solve for x
    x = 90,419.11/428.89
  6. Step 6: Final answer
    x = 210.82

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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.