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Finding the Fourth Proportional to 85.74, 128.76 and 81.89

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Solution

The fourth proportional to 85.74, 128.76 and 81.89 is: 122.97

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.74 : 128.76 = 81.89 : x
  2. Step 2: Convert to fraction form
    85.74/128.76 = 81.89/x
  3. Step 3: Cross multiply
    85.74x = 128.76 × 81.89
  4. Step 4: Simplify right side
    85.74x = 10,543.75
  5. Step 5: Solve for x
    x = 10,543.75/85.74
  6. Step 6: Final answer
    x = 122.97

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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.