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Finding the Fourth Proportional to 85.28, 128.06 and 51.21

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Solution

The fourth proportional to 85.28, 128.06 and 51.21 is: 76.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.28 : 128.06 = 51.21 : x
  2. Step 2: Convert to fraction form
    85.28/128.06 = 51.21/x
  3. Step 3: Cross multiply
    85.28x = 128.06 × 51.21
  4. Step 4: Simplify right side
    85.28x = 6,557.38
  5. Step 5: Solve for x
    x = 6,557.38/85.28
  6. Step 6: Final answer
    x = 76.89

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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.