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Finding the Fourth Proportional to 81, 121.56 and 57

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Solution

The fourth proportional to 81, 121.56 and 57 is: 85.54

Step by Step Solution

  1. Step 1: Write the proportion equation
    81 : 121.56 = 57 : x
  2. Step 2: Convert to fraction form
    81/121.56 = 57/x
  3. Step 3: Cross multiply
    81x = 121.56 × 57
  4. Step 4: Simplify right side
    81x = 6,928.92
  5. Step 5: Solve for x
    x = 6,928.92/81
  6. Step 6: Final answer
    x = 85.54

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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.