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Finding the Fourth Proportional to 81.68, 122.40 and 71.76

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Solution

The fourth proportional to 81.68, 122.40 and 71.76 is: 107.53

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.68 : 122.40 = 71.76 : x
  2. Step 2: Convert to fraction form
    81.68/122.40 = 71.76/x
  3. Step 3: Cross multiply
    81.68x = 122.40 × 71.76
  4. Step 4: Simplify right side
    81.68x = 8,783.42
  5. Step 5: Solve for x
    x = 8,783.42/81.68
  6. Step 6: Final answer
    x = 107.53

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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.