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Finding the Fourth Proportional to 81.05, 121.59 and 57.15

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Solution

The fourth proportional to 81.05, 121.59 and 57.15 is: 85.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.05 : 121.59 = 57.15 : x
  2. Step 2: Convert to fraction form
    81.05/121.59 = 57.15/x
  3. Step 3: Cross multiply
    81.05x = 121.59 × 57.15
  4. Step 4: Simplify right side
    81.05x = 6,948.87
  5. Step 5: Solve for x
    x = 6,948.87/81.05
  6. Step 6: Final answer
    x = 85.74

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.