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Finding the Fourth Proportional to 13.21, 19.78 and 7.79

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Solution

The fourth proportional to 13.21, 19.78 and 7.79 is: 11.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    13.21 : 19.78 = 7.79 : x
  2. Step 2: Convert to fraction form
    13.21/19.78 = 7.79/x
  3. Step 3: Cross multiply
    13.21x = 19.78 × 7.79
  4. Step 4: Simplify right side
    13.21x = 154.09
  5. Step 5: Solve for x
    x = 154.09/13.21
  6. Step 6: Final answer
    x = 11.66

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.