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Finding the Fourth Proportional to 121.78, 168.06 and 86.80

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Solution

The fourth proportional to 121.78, 168.06 and 86.80 is: 119.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    121.78 : 168.06 = 86.80 : x
  2. Step 2: Convert to fraction form
    121.78/168.06 = 86.80/x
  3. Step 3: Cross multiply
    121.78x = 168.06 × 86.80
  4. Step 4: Simplify right side
    121.78x = 14,587.61
  5. Step 5: Solve for x
    x = 14,587.61/121.78
  6. Step 6: Final answer
    x = 119.79

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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.