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Finding the Fourth Proportional to 20.80, 31.18 and 12.78

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Solution

The fourth proportional to 20.80, 31.18 and 12.78 is: 19.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.80 : 31.18 = 12.78 : x
  2. Step 2: Convert to fraction form
    20.80/31.18 = 12.78/x
  3. Step 3: Cross multiply
    20.80x = 31.18 × 12.78
  4. Step 4: Simplify right side
    20.80x = 398.48
  5. Step 5: Solve for x
    x = 398.48/20.80
  6. Step 6: Final answer
    x = 19.16

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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.