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Finding the Fourth Proportional to 121.90, 168.22 and 72.78

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Solution

The fourth proportional to 121.90, 168.22 and 72.78 is: 100.44

Step by Step Solution

  1. Step 1: Write the proportion equation
    121.90 : 168.22 = 72.78 : x
  2. Step 2: Convert to fraction form
    121.90/168.22 = 72.78/x
  3. Step 3: Cross multiply
    121.90x = 168.22 × 72.78
  4. Step 4: Simplify right side
    121.90x = 12,243.05
  5. Step 5: Solve for x
    x = 12,243.05/121.90
  6. Step 6: Final answer
    x = 100.44

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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.