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Finding the Fourth Proportional to 138.76, 208.07 and 81.00

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Solution

The fourth proportional to 138.76, 208.07 and 81.00 is: 121.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.76 : 208.07 = 81.00 : x
  2. Step 2: Convert to fraction form
    138.76/208.07 = 81.00/x
  3. Step 3: Cross multiply
    138.76x = 208.07 × 81.00
  4. Step 4: Simplify right side
    138.76x = 16,852.67
  5. Step 5: Solve for x
    x = 16,852.67/138.76
  6. Step 6: Final answer
    x = 121.45

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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.