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Finding the Fourth Proportional to 99.91, 137.77 and 79.21

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Solution

The fourth proportional to 99.91, 137.77 and 79.21 is: 109.23

Step by Step Solution

  1. Step 1: Write the proportion equation
    99.91 : 137.77 = 79.21 : x
  2. Step 2: Convert to fraction form
    99.91/137.77 = 79.21/x
  3. Step 3: Cross multiply
    99.91x = 137.77 × 79.21
  4. Step 4: Simplify right side
    99.91x = 10,912.76
  5. Step 5: Solve for x
    x = 10,912.76/99.91
  6. Step 6: Final answer
    x = 109.23

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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.