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Finding the Fourth Proportional to 121.86, 168.12 and 90.72

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Solution

The fourth proportional to 121.86, 168.12 and 90.72 is: 125.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    121.86 : 168.12 = 90.72 : x
  2. Step 2: Convert to fraction form
    121.86/168.12 = 90.72/x
  3. Step 3: Cross multiply
    121.86x = 168.12 × 90.72
  4. Step 4: Simplify right side
    121.86x = 15,251.85
  5. Step 5: Solve for x
    x = 15,251.85/121.86
  6. Step 6: Final answer
    x = 125.16

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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.