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Finding the Fourth Proportional to 81.77, 121.91 and 78.71

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Solution

The fourth proportional to 81.77, 121.91 and 78.71 is: 117.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.77 : 121.91 = 78.71 : x
  2. Step 2: Convert to fraction form
    81.77/121.91 = 78.71/x
  3. Step 3: Cross multiply
    81.77x = 121.91 × 78.71
  4. Step 4: Simplify right side
    81.77x = 9,594.53
  5. Step 5: Solve for x
    x = 9,594.53/81.77
  6. Step 6: Final answer
    x = 117.34

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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.