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Finding the Fourth Proportional to 81.42, 122.09 and 40.80

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Solution

The fourth proportional to 81.42, 122.09 and 40.80 is: 61.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.42 : 122.09 = 40.80 : x
  2. Step 2: Convert to fraction form
    81.42/122.09 = 40.80/x
  3. Step 3: Cross multiply
    81.42x = 122.09 × 40.80
  4. Step 4: Simplify right side
    81.42x = 4,981.07
  5. Step 5: Solve for x
    x = 4,981.07/81.42
  6. Step 6: Final answer
    x = 61.18

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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.