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Finding the Fourth Proportional to 138.15, 189.63 and 121.77

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Solution

The fourth proportional to 138.15, 189.63 and 121.77 is: 167.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.15 : 189.63 = 121.77 : x
  2. Step 2: Convert to fraction form
    138.15/189.63 = 121.77/x
  3. Step 3: Cross multiply
    138.15x = 189.63 × 121.77
  4. Step 4: Simplify right side
    138.15x = 23,091.25
  5. Step 5: Solve for x
    x = 23,091.25/138.15
  6. Step 6: Final answer
    x = 167.15

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Why These Related Problems?

These problems maintain the same ratio (1.37) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.