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Finding the Fourth Proportional to 121.72, 167.90 and 78.04

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Solution

The fourth proportional to 121.72, 167.90 and 78.04 is: 107.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    121.72 : 167.90 = 78.04 : x
  2. Step 2: Convert to fraction form
    121.72/167.90 = 78.04/x
  3. Step 3: Cross multiply
    121.72x = 167.90 × 78.04
  4. Step 4: Simplify right side
    121.72x = 13,102.92
  5. Step 5: Solve for x
    x = 13,102.92/121.72
  6. Step 6: Final answer
    x = 107.65

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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.