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Finding the Fourth Proportional to 85.94, 128.13 and 80.78

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Solution

The fourth proportional to 85.94, 128.13 and 80.78 is: 120.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.94 : 128.13 = 80.78 : x
  2. Step 2: Convert to fraction form
    85.94/128.13 = 80.78/x
  3. Step 3: Cross multiply
    85.94x = 128.13 × 80.78
  4. Step 4: Simplify right side
    85.94x = 10,349.30
  5. Step 5: Solve for x
    x = 10,349.30/85.94
  6. Step 6: Final answer
    x = 120.42

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.