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Finding the Fourth Proportional to 13.21, 19.90 and 12.20

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Solution

The fourth proportional to 13.21, 19.90 and 12.20 is: 18.37

Step by Step Solution

  1. Step 1: Write the proportion equation
    13.21 : 19.90 = 12.20 : x
  2. Step 2: Convert to fraction form
    13.21/19.90 = 12.20/x
  3. Step 3: Cross multiply
    13.21x = 19.90 × 12.20
  4. Step 4: Simplify right side
    13.21x = 242.74
  5. Step 5: Solve for x
    x = 242.74/13.21
  6. Step 6: Final answer
    x = 18.37

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Why These Related Problems?

These problems maintain the same ratio (1.51) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.