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Finding the Fourth Proportional to 20.91, 31.20 and 18.21

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Solution

The fourth proportional to 20.91, 31.20 and 18.21 is: 27.17

Step by Step Solution

  1. Step 1: Write the proportion equation
    20.91 : 31.20 = 18.21 : x
  2. Step 2: Convert to fraction form
    20.91/31.20 = 18.21/x
  3. Step 3: Cross multiply
    20.91x = 31.20 × 18.21
  4. Step 4: Simplify right side
    20.91x = 568.15
  5. Step 5: Solve for x
    x = 568.15/20.91
  6. Step 6: Final answer
    x = 27.17

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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.