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Finding the Fourth Proportional to 15.91, 21.96 and 8.64

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Solution

The fourth proportional to 15.91, 21.96 and 8.64 is: 11.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.91 : 21.96 = 8.64 : x
  2. Step 2: Convert to fraction form
    15.91/21.96 = 8.64/x
  3. Step 3: Cross multiply
    15.91x = 21.96 × 8.64
  4. Step 4: Simplify right side
    15.91x = 189.68
  5. Step 5: Solve for x
    x = 189.68/15.91
  6. Step 6: Final answer
    x = 11.92

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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.