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Finding the Fourth Proportional to 85.31, 128.02 and 31.19

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Solution

The fourth proportional to 85.31, 128.02 and 31.19 is: 46.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.31 : 128.02 = 31.19 : x
  2. Step 2: Convert to fraction form
    85.31/128.02 = 31.19/x
  3. Step 3: Cross multiply
    85.31x = 128.02 × 31.19
  4. Step 4: Simplify right side
    85.31x = 3,993.19
  5. Step 5: Solve for x
    x = 3,993.19/85.31
  6. Step 6: Final answer
    x = 46.81

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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.