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Finding the Third Proportional to 378.50 and 390.50

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Solution

The third proportional to 378.50 and 390.50 is: 402.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    378.50 : 390.50 = 390.50 : x
  2. Step 2: Convert to fraction form
    378.50/390.50 = 390.50/x
  3. Step 3: Cross multiply
    378.50x = 390.50 × 390.50
  4. Step 4: Simplify right side
    378.50x = 152,490.25
  5. Step 5: Solve for x
    x = 152,490.25/378.50
  6. Step 6: Final answer
    x = 402.88

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Why These Related Problems?

These problems maintain the same ratio (1.03) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.