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Finding the Fourth Proportional to 142.20, 213.35 and 81.39

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Solution

The fourth proportional to 142.20, 213.35 and 81.39 is: 122.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    142.20 : 213.35 = 81.39 : x
  2. Step 2: Convert to fraction form
    142.20/213.35 = 81.39/x
  3. Step 3: Cross multiply
    142.20x = 213.35 × 81.39
  4. Step 4: Simplify right side
    142.20x = 17,364.56
  5. Step 5: Solve for x
    x = 17,364.56/142.20
  6. Step 6: Final answer
    x = 122.11

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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.