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Finding the Third Proportional to 390.75 and 621.88

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Solution

The third proportional to 390.75 and 621.88 is: 989.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.75 : 621.88 = 621.88 : x
  2. Step 2: Convert to fraction form
    390.75/621.88 = 621.88/x
  3. Step 3: Cross multiply
    390.75x = 621.88 × 621.88
  4. Step 4: Simplify right side
    390.75x = 386,728.52
  5. Step 5: Solve for x
    x = 386,728.52/390.75
  6. Step 6: Final answer
    x = 989.71

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Why These Related Problems?

These problems maintain the same ratio (1.59) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.