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Finding the Fourth Proportional to 85.39, 128 and 31.27

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Solution

The fourth proportional to 85.39, 128 and 31.27 is: 46.87

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.39 : 128 = 31.27 : x
  2. Step 2: Convert to fraction form
    85.39/128 = 31.27/x
  3. Step 3: Cross multiply
    85.39x = 128 × 31.27
  4. Step 4: Simplify right side
    85.39x = 4,002.56
  5. Step 5: Solve for x
    x = 4,002.56/85.39
  6. Step 6: Final answer
    x = 46.87

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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.