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Finding the Fourth Proportional to 20.72, 31.12 and 19.78

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Solution

The fourth proportional to 20.72, 31.12 and 19.78 is: 29.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.72 : 31.12 = 19.78 : x
  2. Step 2: Convert to fraction form
    20.72/31.12 = 19.78/x
  3. Step 3: Cross multiply
    20.72x = 31.12 × 19.78
  4. Step 4: Simplify right side
    20.72x = 615.43
  5. Step 5: Solve for x
    x = 615.43/20.72
  6. Step 6: Final answer
    x = 29.70

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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.