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Finding the Fourth Proportional to 85.12, 128.20 and 71.68

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Solution

The fourth proportional to 85.12, 128.20 and 71.68 is: 107.96

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.12 : 128.20 = 71.68 : x
  2. Step 2: Convert to fraction form
    85.12/128.20 = 71.68/x
  3. Step 3: Cross multiply
    85.12x = 128.20 × 71.68
  4. Step 4: Simplify right side
    85.12x = 9,189.38
  5. Step 5: Solve for x
    x = 9,189.38/85.12
  6. Step 6: Final answer
    x = 107.96

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.