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Finding the Fourth Proportional to 85.59, 128.39 and 77.76

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Solution

The fourth proportional to 85.59, 128.39 and 77.76 is: 116.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.59 : 128.39 = 77.76 : x
  2. Step 2: Convert to fraction form
    85.59/128.39 = 77.76/x
  3. Step 3: Cross multiply
    85.59x = 128.39 × 77.76
  4. Step 4: Simplify right side
    85.59x = 9,983.22
  5. Step 5: Solve for x
    x = 9,983.22/85.59
  6. Step 6: Final answer
    x = 116.64

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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.