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Finding the Fourth Proportional to 30.50, 42.10 and 20.80

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Solution

The fourth proportional to 30.50, 42.10 and 20.80 is: 28.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.50 : 42.10 = 20.80 : x
  2. Step 2: Convert to fraction form
    30.50/42.10 = 20.80/x
  3. Step 3: Cross multiply
    30.50x = 42.10 × 20.80
  4. Step 4: Simplify right side
    30.50x = 875.68
  5. Step 5: Solve for x
    x = 875.68/30.50
  6. Step 6: Final answer
    x = 28.71

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.