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Finding the Fourth Proportional to 15.90, 21.96 and 13.61

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Solution

The fourth proportional to 15.90, 21.96 and 13.61 is: 18.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.90 : 21.96 = 13.61 : x
  2. Step 2: Convert to fraction form
    15.90/21.96 = 13.61/x
  3. Step 3: Cross multiply
    15.90x = 21.96 × 13.61
  4. Step 4: Simplify right side
    15.90x = 298.77
  5. Step 5: Solve for x
    x = 298.77/15.90
  6. Step 6: Final answer
    x = 18.79

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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.