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Finding the Fourth Proportional to 120.57, 166.40 and 81.78

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Solution

The fourth proportional to 120.57, 166.40 and 81.78 is: 112.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    120.57 : 166.40 = 81.78 : x
  2. Step 2: Convert to fraction form
    120.57/166.40 = 81.78/x
  3. Step 3: Cross multiply
    120.57x = 166.40 × 81.78
  4. Step 4: Simplify right side
    120.57x = 13,608.19
  5. Step 5: Solve for x
    x = 13,608.19/120.57
  6. Step 6: Final answer
    x = 112.87

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.