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Finding the Fourth Proportional to 85.87, 128.79 and 31.73

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Solution

The fourth proportional to 85.87, 128.79 and 31.73 is: 47.59

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.87 : 128.79 = 31.73 : x
  2. Step 2: Convert to fraction form
    85.87/128.79 = 31.73/x
  3. Step 3: Cross multiply
    85.87x = 128.79 × 31.73
  4. Step 4: Simplify right side
    85.87x = 4,086.51
  5. Step 5: Solve for x
    x = 4,086.51/85.87
  6. Step 6: Final answer
    x = 47.59

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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.