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Finding the Fourth Proportional to 102.78, 142.02 and 81

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Solution

The fourth proportional to 102.78, 142.02 and 81 is: 111.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    102.78 : 142.02 = 81 : x
  2. Step 2: Convert to fraction form
    102.78/142.02 = 81/x
  3. Step 3: Cross multiply
    102.78x = 142.02 × 81
  4. Step 4: Simplify right side
    102.78x = 11,503.62
  5. Step 5: Solve for x
    x = 11,503.62/102.78
  6. Step 6: Final answer
    x = 111.92

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.