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Finding the Fourth Proportional to 105.91, 145.90 and 81.20

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Solution

The fourth proportional to 105.91, 145.90 and 81.20 is: 111.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    105.91 : 145.90 = 81.20 : x
  2. Step 2: Convert to fraction form
    105.91/145.90 = 81.20/x
  3. Step 3: Cross multiply
    105.91x = 145.90 × 81.20
  4. Step 4: Simplify right side
    105.91x = 11,847.55
  5. Step 5: Solve for x
    x = 11,847.55/105.91
  6. Step 6: Final answer
    x = 111.87

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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.