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Finding the Fourth Proportional to 85.82, 128.88 and 81.05

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Solution

The fourth proportional to 85.82, 128.88 and 81.05 is: 121.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.82 : 128.88 = 81.05 : x
  2. Step 2: Convert to fraction form
    85.82/128.88 = 81.05/x
  3. Step 3: Cross multiply
    85.82x = 128.88 × 81.05
  4. Step 4: Simplify right side
    85.82x = 10,445.08
  5. Step 5: Solve for x
    x = 10,445.08/85.82
  6. Step 6: Final answer
    x = 121.72

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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.