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Finding the Fourth Proportional to 21.08, 31.55 and 20.56

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Solution

The fourth proportional to 21.08, 31.55 and 20.56 is: 30.77

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.08 : 31.55 = 20.56 : x
  2. Step 2: Convert to fraction form
    21.08/31.55 = 20.56/x
  3. Step 3: Cross multiply
    21.08x = 31.55 × 20.56
  4. Step 4: Simplify right side
    21.08x = 648.54
  5. Step 5: Solve for x
    x = 648.54/21.08
  6. Step 6: Final answer
    x = 30.77

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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.