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Finding the Fourth Proportional to 85.72, 128.75 and 51.55

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Solution

The fourth proportional to 85.72, 128.75 and 51.55 is: 77.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.72 : 128.75 = 51.55 : x
  2. Step 2: Convert to fraction form
    85.72/128.75 = 51.55/x
  3. Step 3: Cross multiply
    85.72x = 128.75 × 51.55
  4. Step 4: Simplify right side
    85.72x = 6,636.48
  5. Step 5: Solve for x
    x = 6,636.48/85.72
  6. Step 6: Final answer
    x = 77.42

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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.