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Finding the Fourth Proportional to 85.91, 128.85 and 45.30

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Solution

The fourth proportional to 85.91, 128.85 and 45.30 is: 67.95

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.91 : 128.85 = 45.30 : x
  2. Step 2: Convert to fraction form
    85.91/128.85 = 45.30/x
  3. Step 3: Cross multiply
    85.91x = 128.85 × 45.30
  4. Step 4: Simplify right side
    85.91x = 5,836.91
  5. Step 5: Solve for x
    x = 5,836.91/85.91
  6. Step 6: Final answer
    x = 67.95

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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.