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Finding the Fourth Proportional to 85.20, 128.27 and 77.64

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Solution

The fourth proportional to 85.20, 128.27 and 77.64 is: 116.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.20 : 128.27 = 77.64 : x
  2. Step 2: Convert to fraction form
    85.20/128.27 = 77.64/x
  3. Step 3: Cross multiply
    85.20x = 128.27 × 77.64
  4. Step 4: Simplify right side
    85.20x = 9,958.49
  5. Step 5: Solve for x
    x = 9,958.49/85.20
  6. Step 6: Final answer
    x = 116.88

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.