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Finding the Fourth Proportional to 85.49, 128.23 and 81.16

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Solution

The fourth proportional to 85.49, 128.23 and 81.16 is: 121.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.49 : 128.23 = 81.16 : x
  2. Step 2: Convert to fraction form
    85.49/128.23 = 81.16/x
  3. Step 3: Cross multiply
    85.49x = 128.23 × 81.16
  4. Step 4: Simplify right side
    85.49x = 10,407.44
  5. Step 5: Solve for x
    x = 10,407.44/85.49
  6. Step 6: Final answer
    x = 121.74

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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.