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Finding the Fourth Proportional to 81.09, 121.64 and 57.20

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Solution

The fourth proportional to 81.09, 121.64 and 57.20 is: 85.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.09 : 121.64 = 57.20 : x
  2. Step 2: Convert to fraction form
    81.09/121.64 = 57.20/x
  3. Step 3: Cross multiply
    81.09x = 121.64 × 57.20
  4. Step 4: Simplify right side
    81.09x = 6,956.91
  5. Step 5: Solve for x
    x = 6,956.91/81.09
  6. Step 6: Final answer
    x = 85.79

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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.