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Finding the Fourth Proportional to 81, 121.16 and 61.78

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Solution

The fourth proportional to 81, 121.16 and 61.78 is: 92.41

Step by Step Solution

  1. Step 1: Write the proportion equation
    81 : 121.16 = 61.78 : x
  2. Step 2: Convert to fraction form
    81/121.16 = 61.78/x
  3. Step 3: Cross multiply
    81x = 121.16 × 61.78
  4. Step 4: Simplify right side
    81x = 7,485.26
  5. Step 5: Solve for x
    x = 7,485.26/81
  6. Step 6: Final answer
    x = 92.41

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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.