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Finding the Fourth Proportional to 81.90, 113.16 and 65.65

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Solution

The fourth proportional to 81.90, 113.16 and 65.65 is: 90.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.90 : 113.16 = 65.65 : x
  2. Step 2: Convert to fraction form
    81.90/113.16 = 65.65/x
  3. Step 3: Cross multiply
    81.90x = 113.16 × 65.65
  4. Step 4: Simplify right side
    81.90x = 7,428.95
  5. Step 5: Solve for x
    x = 7,428.95/81.90
  6. Step 6: Final answer
    x = 90.71

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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.