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Finding the Fourth Proportional to 31.80, 47.71 and 20.42

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Solution

The fourth proportional to 31.80, 47.71 and 20.42 is: 30.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.80 : 47.71 = 20.42 : x
  2. Step 2: Convert to fraction form
    31.80/47.71 = 20.42/x
  3. Step 3: Cross multiply
    31.80x = 47.71 × 20.42
  4. Step 4: Simplify right side
    31.80x = 974.24
  5. Step 5: Solve for x
    x = 974.24/31.80
  6. Step 6: Final answer
    x = 30.64

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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.