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Finding the Fourth Proportional to 81.40, 122.06 and 71.79

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Solution

The fourth proportional to 81.40, 122.06 and 71.79 is: 107.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.40 : 122.06 = 71.79 : x
  2. Step 2: Convert to fraction form
    81.40/122.06 = 71.79/x
  3. Step 3: Cross multiply
    81.40x = 122.06 × 71.79
  4. Step 4: Simplify right side
    81.40x = 8,762.63
  5. Step 5: Solve for x
    x = 8,762.63/81.40
  6. Step 6: Final answer
    x = 107.65

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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.