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Finding the Fourth Proportional to 15.20, 20.91 and 11.55

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Solution

The fourth proportional to 15.20, 20.91 and 11.55 is: 15.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.20 : 20.91 = 11.55 : x
  2. Step 2: Convert to fraction form
    15.20/20.91 = 11.55/x
  3. Step 3: Cross multiply
    15.20x = 20.91 × 11.55
  4. Step 4: Simplify right side
    15.20x = 241.51
  5. Step 5: Solve for x
    x = 241.51/15.20
  6. Step 6: Final answer
    x = 15.89

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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.