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Finding the Fourth Proportional to 85.90, 128.15 and 82.06

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Solution

The fourth proportional to 85.90, 128.15 and 82.06 is: 122.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.90 : 128.15 = 82.06 : x
  2. Step 2: Convert to fraction form
    85.90/128.15 = 82.06/x
  3. Step 3: Cross multiply
    85.90x = 128.15 × 82.06
  4. Step 4: Simplify right side
    85.90x = 10,515.99
  5. Step 5: Solve for x
    x = 10,515.99/85.90
  6. Step 6: Final answer
    x = 122.42

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.