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Finding the Fourth Proportional to 21.91, 30.21 and 15

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Solution

The fourth proportional to 21.91, 30.21 and 15 is: 20.68

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.91 : 30.21 = 15 : x
  2. Step 2: Convert to fraction form
    21.91/30.21 = 15/x
  3. Step 3: Cross multiply
    21.91x = 30.21 × 15
  4. Step 4: Simplify right side
    21.91x = 453.15
  5. Step 5: Solve for x
    x = 453.15/21.91
  6. Step 6: Final answer
    x = 20.68

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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.