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Finding the Fourth Proportional to 11.45, 15.78 and 8.21

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Solution

The fourth proportional to 11.45, 15.78 and 8.21 is: 11.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    11.45 : 15.78 = 8.21 : x
  2. Step 2: Convert to fraction form
    11.45/15.78 = 8.21/x
  3. Step 3: Cross multiply
    11.45x = 15.78 × 8.21
  4. Step 4: Simplify right side
    11.45x = 129.47
  5. Step 5: Solve for x
    x = 129.47/11.45
  6. Step 6: Final answer
    x = 11.31

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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.