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Finding the Fourth Proportional to 85.20, 117.50 and 81.15

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Solution

The fourth proportional to 85.20, 117.50 and 81.15 is: 111.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.20 : 117.50 = 81.15 : x
  2. Step 2: Convert to fraction form
    85.20/117.50 = 81.15/x
  3. Step 3: Cross multiply
    85.20x = 117.50 × 81.15
  4. Step 4: Simplify right side
    85.20x = 9,534.72
  5. Step 5: Solve for x
    x = 9,534.72/85.20
  6. Step 6: Final answer
    x = 111.91

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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.