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Finding the Fourth Proportional to 138, 207.18 and 120.90

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Solution

The fourth proportional to 138, 207.18 and 120.90 is: 181.51

Step by Step Solution

  1. Step 1: Write the proportion equation
    138 : 207.18 = 120.90 : x
  2. Step 2: Convert to fraction form
    138/207.18 = 120.90/x
  3. Step 3: Cross multiply
    138x = 207.18 × 120.90
  4. Step 4: Simplify right side
    138x = 25,048.06
  5. Step 5: Solve for x
    x = 25,048.06/138
  6. Step 6: Final answer
    x = 181.51

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.