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Finding the Fourth Proportional to 81.24, 121.52 and 80

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Solution

The fourth proportional to 81.24, 121.52 and 80 is: 119.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.24 : 121.52 = 80 : x
  2. Step 2: Convert to fraction form
    81.24/121.52 = 80/x
  3. Step 3: Cross multiply
    81.24x = 121.52 × 80
  4. Step 4: Simplify right side
    81.24x = 9,721.60
  5. Step 5: Solve for x
    x = 9,721.60/81.24
  6. Step 6: Final answer
    x = 119.67

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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.