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Finding the Fourth Proportional to 20.87, 31.29 and 6.42

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Solution

The fourth proportional to 20.87, 31.29 and 6.42 is: 9.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.87 : 31.29 = 6.42 : x
  2. Step 2: Convert to fraction form
    20.87/31.29 = 6.42/x
  3. Step 3: Cross multiply
    20.87x = 31.29 × 6.42
  4. Step 4: Simplify right side
    20.87x = 201.02
  5. Step 5: Solve for x
    x = 201.02/20.87
  6. Step 6: Final answer
    x = 9.63

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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.