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Finding the Fourth Proportional to 81.86, 121.96 and 77.18

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Solution

The fourth proportional to 81.86, 121.96 and 77.18 is: 114.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.86 : 121.96 = 77.18 : x
  2. Step 2: Convert to fraction form
    81.86/121.96 = 77.18/x
  3. Step 3: Cross multiply
    81.86x = 121.96 × 77.18
  4. Step 4: Simplify right side
    81.86x = 9,412.87
  5. Step 5: Solve for x
    x = 9,412.87/81.86
  6. Step 6: Final answer
    x = 114.99

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.