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Finding the Fourth Proportional to 85.42, 128.13 and 31.31

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Solution

The fourth proportional to 85.42, 128.13 and 31.31 is: 46.97

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.42 : 128.13 = 31.31 : x
  2. Step 2: Convert to fraction form
    85.42/128.13 = 31.31/x
  3. Step 3: Cross multiply
    85.42x = 128.13 × 31.31
  4. Step 4: Simplify right side
    85.42x = 4,011.75
  5. Step 5: Solve for x
    x = 4,011.75/85.42
  6. Step 6: Final answer
    x = 46.97

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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.