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Finding the Fourth Proportional to 209.10, 288.54 and 121.78

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Solution

The fourth proportional to 209.10, 288.54 and 121.78 is: 168.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    209.10 : 288.54 = 121.78 : x
  2. Step 2: Convert to fraction form
    209.10/288.54 = 121.78/x
  3. Step 3: Cross multiply
    209.10x = 288.54 × 121.78
  4. Step 4: Simplify right side
    209.10x = 35,138.40
  5. Step 5: Solve for x
    x = 35,138.40/209.10
  6. Step 6: Final answer
    x = 168.05

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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.