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Finding the Fourth Proportional to 30.57, 42.20 and 20.87

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Solution

The fourth proportional to 30.57, 42.20 and 20.87 is: 28.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    30.57 : 42.20 = 20.87 : x
  2. Step 2: Convert to fraction form
    30.57/42.20 = 20.87/x
  3. Step 3: Cross multiply
    30.57x = 42.20 × 20.87
  4. Step 4: Simplify right side
    30.57x = 880.40
  5. Step 5: Solve for x
    x = 880.40/30.57
  6. Step 6: Final answer
    x = 28.80

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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.