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Finding the Fourth Proportional to 81.48, 121.20 and 81.21

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Solution

The fourth proportional to 81.48, 121.20 and 81.21 is: 120.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.48 : 121.20 = 81.21 : x
  2. Step 2: Convert to fraction form
    81.48/121.20 = 81.21/x
  3. Step 3: Cross multiply
    81.48x = 121.20 × 81.21
  4. Step 4: Simplify right side
    81.48x = 9,842.65
  5. Step 5: Solve for x
    x = 9,842.65/81.48
  6. Step 6: Final answer
    x = 120.80

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.