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Finding the Fourth Proportional to 85.60, 128.16 and 80.68

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Solution

The fourth proportional to 85.60, 128.16 and 80.68 is: 120.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.60 : 128.16 = 80.68 : x
  2. Step 2: Convert to fraction form
    85.60/128.16 = 80.68/x
  3. Step 3: Cross multiply
    85.60x = 128.16 × 80.68
  4. Step 4: Simplify right side
    85.60x = 10,339.95
  5. Step 5: Solve for x
    x = 10,339.95/85.60
  6. Step 6: Final answer
    x = 120.79

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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.