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Finding the Fourth Proportional to 142.23, 213.39 and 81.21

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Solution

The fourth proportional to 142.23, 213.39 and 81.21 is: 121.84

Step by Step Solution

  1. Step 1: Write the proportion equation
    142.23 : 213.39 = 81.21 : x
  2. Step 2: Convert to fraction form
    142.23/213.39 = 81.21/x
  3. Step 3: Cross multiply
    142.23x = 213.39 × 81.21
  4. Step 4: Simplify right side
    142.23x = 17,329.40
  5. Step 5: Solve for x
    x = 17,329.40/142.23
  6. Step 6: Final answer
    x = 121.84

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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.