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Finding the Fourth Proportional to 15.21, 20.98 and 13.28

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Solution

The fourth proportional to 15.21, 20.98 and 13.28 is: 18.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.21 : 20.98 = 13.28 : x
  2. Step 2: Convert to fraction form
    15.21/20.98 = 13.28/x
  3. Step 3: Cross multiply
    15.21x = 20.98 × 13.28
  4. Step 4: Simplify right side
    15.21x = 278.61
  5. Step 5: Solve for x
    x = 278.61/15.21
  6. Step 6: Final answer
    x = 18.32

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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.