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Finding the Fourth Proportional to 31.28, 43.40 and 30.20

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Solution

The fourth proportional to 31.28, 43.40 and 30.20 is: 41.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.28 : 43.40 = 30.20 : x
  2. Step 2: Convert to fraction form
    31.28/43.40 = 30.20/x
  3. Step 3: Cross multiply
    31.28x = 43.40 × 30.20
  4. Step 4: Simplify right side
    31.28x = 1,310.68
  5. Step 5: Solve for x
    x = 1,310.68/31.28
  6. Step 6: Final answer
    x = 41.90

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Why These Related Problems?

These problems maintain the same ratio (1.39) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.