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Finding the Fourth Proportional to 21.08, 31.42 and 20.42

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Solution

The fourth proportional to 21.08, 31.42 and 20.42 is: 30.44

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.08 : 31.42 = 20.42 : x
  2. Step 2: Convert to fraction form
    21.08/31.42 = 20.42/x
  3. Step 3: Cross multiply
    21.08x = 31.42 × 20.42
  4. Step 4: Simplify right side
    21.08x = 641.60
  5. Step 5: Solve for x
    x = 641.60/21.08
  6. Step 6: Final answer
    x = 30.44

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.