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Finding the Fourth Proportional to 80.91, 111.56 and 65.31

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Solution

The fourth proportional to 80.91, 111.56 and 65.31 is: 90.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    80.91 : 111.56 = 65.31 : x
  2. Step 2: Convert to fraction form
    80.91/111.56 = 65.31/x
  3. Step 3: Cross multiply
    80.91x = 111.56 × 65.31
  4. Step 4: Simplify right side
    80.91x = 7,285.66
  5. Step 5: Solve for x
    x = 7,285.66/80.91
  6. Step 6: Final answer
    x = 90.05

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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.