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Finding the Fourth Proportional to 85.40, 128.17 and 51.17

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Solution

The fourth proportional to 85.40, 128.17 and 51.17 is: 76.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.40 : 128.17 = 51.17 : x
  2. Step 2: Convert to fraction form
    85.40/128.17 = 51.17/x
  3. Step 3: Cross multiply
    85.40x = 128.17 × 51.17
  4. Step 4: Simplify right side
    85.40x = 6,557.59
  5. Step 5: Solve for x
    x = 6,557.59/85.40
  6. Step 6: Final answer
    x = 76.78

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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.