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Finding the Fourth Proportional to 100.61, 138.92 and 78.84

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Solution

The fourth proportional to 100.61, 138.92 and 78.84 is: 108.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.61 : 138.92 = 78.84 : x
  2. Step 2: Convert to fraction form
    100.61/138.92 = 78.84/x
  3. Step 3: Cross multiply
    100.61x = 138.92 × 78.84
  4. Step 4: Simplify right side
    100.61x = 10,952.45
  5. Step 5: Solve for x
    x = 10,952.45/100.61
  6. Step 6: Final answer
    x = 108.86

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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.