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Finding the Fourth Proportional to 85.20, 127.79 and 21.07

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Solution

The fourth proportional to 85.20, 127.79 and 21.07 is: 31.61

Step by Step Solution

  1. Step 1: Write the proportion equation
    85.20 : 127.79 = 21.07 : x
  2. Step 2: Convert to fraction form
    85.20/127.79 = 21.07/x
  3. Step 3: Cross multiply
    85.20x = 127.79 × 21.07
  4. Step 4: Simplify right side
    85.20x = 2,692.75
  5. Step 5: Solve for x
    x = 2,692.75/85.20
  6. Step 6: Final answer
    x = 31.61

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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.