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Finding the Fourth Proportional to 20.95, 31.38 and 12.91

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Solution

The fourth proportional to 20.95, 31.38 and 12.91 is: 19.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.95 : 31.38 = 12.91 : x
  2. Step 2: Convert to fraction form
    20.95/31.38 = 12.91/x
  3. Step 3: Cross multiply
    20.95x = 31.38 × 12.91
  4. Step 4: Simplify right side
    20.95x = 405.12
  5. Step 5: Solve for x
    x = 405.12/20.95
  6. Step 6: Final answer
    x = 19.34

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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.