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Finding the Fourth Proportional to 100.47, 138.63 and 86.78

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Solution

The fourth proportional to 100.47, 138.63 and 86.78 is: 119.73

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.47 : 138.63 = 86.78 : x
  2. Step 2: Convert to fraction form
    100.47/138.63 = 86.78/x
  3. Step 3: Cross multiply
    100.47x = 138.63 × 86.78
  4. Step 4: Simplify right side
    100.47x = 12,029.62
  5. Step 5: Solve for x
    x = 12,029.62/100.47
  6. Step 6: Final answer
    x = 119.73

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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.