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Finding the Fourth Proportional to 15.81, 21.75 and 12.88

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Solution

The fourth proportional to 15.81, 21.75 and 12.88 is: 17.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.81 : 21.75 = 12.88 : x
  2. Step 2: Convert to fraction form
    15.81/21.75 = 12.88/x
  3. Step 3: Cross multiply
    15.81x = 21.75 × 12.88
  4. Step 4: Simplify right side
    15.81x = 279.97
  5. Step 5: Solve for x
    x = 279.97/15.81
  6. Step 6: Final answer
    x = 17.71

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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.