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Finding the Third Proportional to 387.28 and 421.45

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Solution

The third proportional to 387.28 and 421.45 is: 458.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    387.28 : 421.45 = 421.45 : x
  2. Step 2: Convert to fraction form
    387.28/421.45 = 421.45/x
  3. Step 3: Cross multiply
    387.28x = 421.45 × 421.45
  4. Step 4: Simplify right side
    387.28x = 177,622.74
  5. Step 5: Solve for x
    x = 177,622.74/387.28
  6. Step 6: Final answer
    x = 458.64

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Why These Related Problems?

These problems maintain the same ratio (1.09) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.