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Finding the Third Proportional to 3.90 and 6.21

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Solution

The third proportional to 3.90 and 6.21 is: 9.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    3.90 : 6.21 = 6.21 : x
  2. Step 2: Convert to fraction form
    3.90/6.21 = 6.21/x
  3. Step 3: Cross multiply
    3.90x = 6.21 × 6.21
  4. Step 4: Simplify right side
    3.90x = 38.57
  5. Step 5: Solve for x
    x = 38.57/3.90
  6. Step 6: Final answer
    x = 9.90

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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.