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Finding the Fourth Proportional to 100.19, 138.06 and 81.78

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Solution

The fourth proportional to 100.19, 138.06 and 81.78 is: 112.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.19 : 138.06 = 81.78 : x
  2. Step 2: Convert to fraction form
    100.19/138.06 = 81.78/x
  3. Step 3: Cross multiply
    100.19x = 138.06 × 81.78
  4. Step 4: Simplify right side
    100.19x = 11,290.55
  5. Step 5: Solve for x
    x = 11,290.55/100.19
  6. Step 6: Final answer
    x = 112.70

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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.