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Finding the Fourth Proportional to 90.85, 135.96 and 77.28

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Solution

The fourth proportional to 90.85, 135.96 and 77.28 is: 115.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    90.85 : 135.96 = 77.28 : x
  2. Step 2: Convert to fraction form
    90.85/135.96 = 77.28/x
  3. Step 3: Cross multiply
    90.85x = 135.96 × 77.28
  4. Step 4: Simplify right side
    90.85x = 10,506.99
  5. Step 5: Solve for x
    x = 10,506.99/90.85
  6. Step 6: Final answer
    x = 115.65

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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.