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Finding the Fourth Proportional to 21.11, 31.64 and 13.87

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Solution

The fourth proportional to 21.11, 31.64 and 13.87 is: 20.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.11 : 31.64 = 13.87 : x
  2. Step 2: Convert to fraction form
    21.11/31.64 = 13.87/x
  3. Step 3: Cross multiply
    21.11x = 31.64 × 13.87
  4. Step 4: Simplify right side
    21.11x = 438.69
  5. Step 5: Solve for x
    x = 438.69/21.11
  6. Step 6: Final answer
    x = 20.78

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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.