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Finding the Fourth Proportional to 15.69, 21.65 and 8.78

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Solution

The fourth proportional to 15.69, 21.65 and 8.78 is: 12.11

Step by Step Solution

  1. Step 1: Write the proportion equation
    15.69 : 21.65 = 8.78 : x
  2. Step 2: Convert to fraction form
    15.69/21.65 = 8.78/x
  3. Step 3: Cross multiply
    15.69x = 21.65 × 8.78
  4. Step 4: Simplify right side
    15.69x = 189.96
  5. Step 5: Solve for x
    x = 189.96/15.69
  6. Step 6: Final answer
    x = 12.11

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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.