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Finding the Fourth Proportional to 121.78, 168.05 and 66.51

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Solution

The fourth proportional to 121.78, 168.05 and 66.51 is: 91.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    121.78 : 168.05 = 66.51 : x
  2. Step 2: Convert to fraction form
    121.78/168.05 = 66.51/x
  3. Step 3: Cross multiply
    121.78x = 168.05 × 66.51
  4. Step 4: Simplify right side
    121.78x = 11,177.46
  5. Step 5: Solve for x
    x = 11,177.46/121.78
  6. Step 6: Final answer
    x = 91.79

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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.