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Finding the Third Proportional to 390.21 and 816.49

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Solution

The third proportional to 390.21 and 816.49 is: 1,708.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    390.21 : 816.49 = 816.49 : x
  2. Step 2: Convert to fraction form
    390.21/816.49 = 816.49/x
  3. Step 3: Cross multiply
    390.21x = 816.49 × 816.49
  4. Step 4: Simplify right side
    390.21x = 666,649.92
  5. Step 5: Solve for x
    x = 666,649.92/390.21
  6. Step 6: Final answer
    x = 1,708.45

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Why These Related Problems?

These problems maintain the same ratio (2.09) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.