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Finding the Fourth Proportional to 86.79, 129.97 and 85.31

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Solution

The fourth proportional to 86.79, 129.97 and 85.31 is: 127.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.79 : 129.97 = 85.31 : x
  2. Step 2: Convert to fraction form
    86.79/129.97 = 85.31/x
  3. Step 3: Cross multiply
    86.79x = 129.97 × 85.31
  4. Step 4: Simplify right side
    86.79x = 11,086.66
  5. Step 5: Solve for x
    x = 11,086.66/86.79
  6. Step 6: Final answer
    x = 127.74

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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.