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Finding the Fourth Proportional to 121.72, 167.95 and 78.05

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Solution

The fourth proportional to 121.72, 167.95 and 78.05 is: 107.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    121.72 : 167.95 = 78.05 : x
  2. Step 2: Convert to fraction form
    121.72/167.95 = 78.05/x
  3. Step 3: Cross multiply
    121.72x = 167.95 × 78.05
  4. Step 4: Simplify right side
    121.72x = 13,108.50
  5. Step 5: Solve for x
    x = 13,108.50/121.72
  6. Step 6: Final answer
    x = 107.69

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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.