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Finding the Fourth Proportional to 81.42, 111.76 and 77.90

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Solution

The fourth proportional to 81.42, 111.76 and 77.90 is: 106.93

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.42 : 111.76 = 77.90 : x
  2. Step 2: Convert to fraction form
    81.42/111.76 = 77.90/x
  3. Step 3: Cross multiply
    81.42x = 111.76 × 77.90
  4. Step 4: Simplify right side
    81.42x = 8,706.10
  5. Step 5: Solve for x
    x = 8,706.10/81.42
  6. Step 6: Final answer
    x = 106.93

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Why These Related Problems?

These problems maintain the same ratio (1.37) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.