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Finding the Fourth Proportional to 85.57, 128.23 and 42.85

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Solution

The fourth proportional to 85.57, 128.23 and 42.85 is: 64.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.57 : 128.23 = 42.85 : x
  2. Step 2: Convert to fraction form
    85.57/128.23 = 42.85/x
  3. Step 3: Cross multiply
    85.57x = 128.23 × 42.85
  4. Step 4: Simplify right side
    85.57x = 5,494.66
  5. Step 5: Solve for x
    x = 5,494.66/85.57
  6. Step 6: Final answer
    x = 64.21

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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.