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Finding the Fourth Proportional to 30.43, 42.20 and 28.70

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Solution

The fourth proportional to 30.43, 42.20 and 28.70 is: 39.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.43 : 42.20 = 28.70 : x
  2. Step 2: Convert to fraction form
    30.43/42.20 = 28.70/x
  3. Step 3: Cross multiply
    30.43x = 42.20 × 28.70
  4. Step 4: Simplify right side
    30.43x = 1,211.21
  5. Step 5: Solve for x
    x = 1,211.21/30.43
  6. Step 6: Final answer
    x = 39.81

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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.