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Finding the Fourth Proportional to 85.72, 128.53 and 30.85

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Solution

The fourth proportional to 85.72, 128.53 and 30.85 is: 46.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.72 : 128.53 = 30.85 : x
  2. Step 2: Convert to fraction form
    85.72/128.53 = 30.85/x
  3. Step 3: Cross multiply
    85.72x = 128.53 × 30.85
  4. Step 4: Simplify right side
    85.72x = 3,964.35
  5. Step 5: Solve for x
    x = 3,964.35/85.72
  6. Step 6: Final answer
    x = 46.25

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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.