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Finding the Fourth Proportional to 81.09, 111.77 and 66.40

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Solution

The fourth proportional to 81.09, 111.77 and 66.40 is: 91.52

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.09 : 111.77 = 66.40 : x
  2. Step 2: Convert to fraction form
    81.09/111.77 = 66.40/x
  3. Step 3: Cross multiply
    81.09x = 111.77 × 66.40
  4. Step 4: Simplify right side
    81.09x = 7,421.53
  5. Step 5: Solve for x
    x = 7,421.53/81.09
  6. Step 6: Final answer
    x = 91.52

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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.