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Finding the Fourth Proportional to 81, 111.78 and 65.48

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Solution

The fourth proportional to 81, 111.78 and 65.48 is: 90.36

Step by Step Solution

  1. Step 1: Write the proportion equation
    81 : 111.78 = 65.48 : x
  2. Step 2: Convert to fraction form
    81/111.78 = 65.48/x
  3. Step 3: Cross multiply
    81x = 111.78 × 65.48
  4. Step 4: Simplify right side
    81x = 7,318.80
  5. Step 5: Solve for x
    x = 7,318.80/81
  6. Step 6: Final answer
    x = 90.36

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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.