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Finding the Fourth Proportional to 18.89, 28.40 and 13.21

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Solution

The fourth proportional to 18.89, 28.40 and 13.21 is: 19.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    18.89 : 28.40 = 13.21 : x
  2. Step 2: Convert to fraction form
    18.89/28.40 = 13.21/x
  3. Step 3: Cross multiply
    18.89x = 28.40 × 13.21
  4. Step 4: Simplify right side
    18.89x = 375.10
  5. Step 5: Solve for x
    x = 375.10/18.89
  6. Step 6: Final answer
    x = 19.86

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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.