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Finding the Fourth Proportional to 85.79, 128.60 and 51.56

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Solution

The fourth proportional to 85.79, 128.60 and 51.56 is: 77.29

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.79 : 128.60 = 51.56 : x
  2. Step 2: Convert to fraction form
    85.79/128.60 = 51.56/x
  3. Step 3: Cross multiply
    85.79x = 128.60 × 51.56
  4. Step 4: Simplify right side
    85.79x = 6,630.62
  5. Step 5: Solve for x
    x = 6,630.62/85.79
  6. Step 6: Final answer
    x = 77.29

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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.