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Finding the Fourth Proportional to 85.28, 127.85 and 31.21

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Solution

The fourth proportional to 85.28, 127.85 and 31.21 is: 46.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.28 : 127.85 = 31.21 : x
  2. Step 2: Convert to fraction form
    85.28/127.85 = 31.21/x
  3. Step 3: Cross multiply
    85.28x = 127.85 × 31.21
  4. Step 4: Simplify right side
    85.28x = 3,989.72
  5. Step 5: Solve for x
    x = 3,989.72/85.28
  6. Step 6: Final answer
    x = 46.79

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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.