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Finding the Third Proportional to 128 and 138.50

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Solution

The third proportional to 128 and 138.50 is: 149.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    128 : 138.50 = 138.50 : x
  2. Step 2: Convert to fraction form
    128/138.50 = 138.50/x
  3. Step 3: Cross multiply
    128x = 138.50 × 138.50
  4. Step 4: Simplify right side
    128x = 19,182.25
  5. Step 5: Solve for x
    x = 19,182.25/128
  6. Step 6: Final answer
    x = 149.86

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Why These Related Problems?

These problems maintain the same ratio (1.08) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.