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Finding the Fourth Proportional to 85.89, 128.19 and 77.69

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Solution

The fourth proportional to 85.89, 128.19 and 77.69 is: 115.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.89 : 128.19 = 77.69 : x
  2. Step 2: Convert to fraction form
    85.89/128.19 = 77.69/x
  3. Step 3: Cross multiply
    85.89x = 128.19 × 77.69
  4. Step 4: Simplify right side
    85.89x = 9,959.08
  5. Step 5: Solve for x
    x = 9,959.08/85.89
  6. Step 6: Final answer
    x = 115.95

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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.