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Finding the Fourth Proportional to 85.15, 117.31 and 81.28

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Solution

The fourth proportional to 85.15, 117.31 and 81.28 is: 111.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.15 : 117.31 = 81.28 : x
  2. Step 2: Convert to fraction form
    85.15/117.31 = 81.28/x
  3. Step 3: Cross multiply
    85.15x = 117.31 × 81.28
  4. Step 4: Simplify right side
    85.15x = 9,534.96
  5. Step 5: Solve for x
    x = 9,534.96/85.15
  6. Step 6: Final answer
    x = 111.98

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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.