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Finding the Fourth Proportional to 100.71, 138.87 and 81

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Solution

The fourth proportional to 100.71, 138.87 and 81 is: 111.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.71 : 138.87 = 81 : x
  2. Step 2: Convert to fraction form
    100.71/138.87 = 81/x
  3. Step 3: Cross multiply
    100.71x = 138.87 × 81
  4. Step 4: Simplify right side
    100.71x = 11,248.47
  5. Step 5: Solve for x
    x = 11,248.47/100.71
  6. Step 6: Final answer
    x = 111.69

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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.