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Finding the Fourth Proportional to 142.31, 213.30 and 81.31

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Solution

The fourth proportional to 142.31, 213.30 and 81.31 is: 121.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    142.31 : 213.30 = 81.31 : x
  2. Step 2: Convert to fraction form
    142.31/213.30 = 81.31/x
  3. Step 3: Cross multiply
    142.31x = 213.30 × 81.31
  4. Step 4: Simplify right side
    142.31x = 17,343.09
  5. Step 5: Solve for x
    x = 17,343.09/142.31
  6. Step 6: Final answer
    x = 121.87

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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.