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Finding the Third Proportional to 128.78 and 286.35

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Solution

The third proportional to 128.78 and 286.35 is: 636.72

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.78 : 286.35 = 286.35 : x
  2. Step 2: Convert to fraction form
    128.78/286.35 = 286.35/x
  3. Step 3: Cross multiply
    128.78x = 286.35 × 286.35
  4. Step 4: Simplify right side
    128.78x = 81,994.98
  5. Step 5: Solve for x
    x = 81,994.98/128.78
  6. Step 6: Final answer
    x = 636.72

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Why These Related Problems?

These problems maintain the same ratio (2.22) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.