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Finding the Fourth Proportional to 121.80, 168.00 and 78.11

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Solution

The fourth proportional to 121.80, 168.00 and 78.11 is: 107.74

Step by Step Solution

  1. Step 1: Write the proportion equation
    121.80 : 168.00 = 78.11 : x
  2. Step 2: Convert to fraction form
    121.80/168.00 = 78.11/x
  3. Step 3: Cross multiply
    121.80x = 168.00 × 78.11
  4. Step 4: Simplify right side
    121.80x = 13,122.61
  5. Step 5: Solve for x
    x = 13,122.61/121.80
  6. Step 6: Final answer
    x = 107.74

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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.