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Finding the Fourth Proportional to 85.81, 128.79 and 82.16

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Solution

The fourth proportional to 85.81, 128.79 and 82.16 is: 123.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.81 : 128.79 = 82.16 : x
  2. Step 2: Convert to fraction form
    85.81/128.79 = 82.16/x
  3. Step 3: Cross multiply
    85.81x = 128.79 × 82.16
  4. Step 4: Simplify right side
    85.81x = 10,581.95
  5. Step 5: Solve for x
    x = 10,581.95/85.81
  6. Step 6: Final answer
    x = 123.32

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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.