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Finding the Fourth Proportional to 121.86, 168.21 and 85.05

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Solution

The fourth proportional to 121.86, 168.21 and 85.05 is: 117.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    121.86 : 168.21 = 85.05 : x
  2. Step 2: Convert to fraction form
    121.86/168.21 = 85.05/x
  3. Step 3: Cross multiply
    121.86x = 168.21 × 85.05
  4. Step 4: Simplify right side
    121.86x = 14,306.26
  5. Step 5: Solve for x
    x = 14,306.26/121.86
  6. Step 6: Final answer
    x = 117.40

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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.