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Finding the Fourth Proportional to 81.42, 121.82 and 47.21

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Solution

The fourth proportional to 81.42, 121.82 and 47.21 is: 70.62

Step by Step Solution

  1. Step 1: Write the proportion equation
    81.42 : 121.82 = 47.21 : x
  2. Step 2: Convert to fraction form
    81.42/121.82 = 47.21/x
  3. Step 3: Cross multiply
    81.42x = 121.82 × 47.21
  4. Step 4: Simplify right side
    81.42x = 5,750.28
  5. Step 5: Solve for x
    x = 5,750.28/81.42
  6. Step 6: Final answer
    x = 70.62

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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.