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Finding the Fourth Proportional to 81.75, 121.89 and 77.16

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Solution

The fourth proportional to 81.75, 121.89 and 77.16 is: 115.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.75 : 121.89 = 77.16 : x
  2. Step 2: Convert to fraction form
    81.75/121.89 = 77.16/x
  3. Step 3: Cross multiply
    81.75x = 121.89 × 77.16
  4. Step 4: Simplify right side
    81.75x = 9,405.03
  5. Step 5: Solve for x
    x = 9,405.03/81.75
  6. Step 6: Final answer
    x = 115.05

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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.