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Finding the Fourth Proportional to 99.72, 137.81 and 77.85

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Solution

The fourth proportional to 99.72, 137.81 and 77.85 is: 107.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    99.72 : 137.81 = 77.85 : x
  2. Step 2: Convert to fraction form
    99.72/137.81 = 77.85/x
  3. Step 3: Cross multiply
    99.72x = 137.81 × 77.85
  4. Step 4: Simplify right side
    99.72x = 10,728.70
  5. Step 5: Solve for x
    x = 10,728.70/99.72
  6. Step 6: Final answer
    x = 107.59

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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.