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Finding the Third Proportional to 3.90 and 4.20

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Solution

The third proportional to 3.90 and 4.20 is: 4.53

Step by Step Solution

  1. Step 1: Write the proportion equation
    3.90 : 4.20 = 4.20 : x
  2. Step 2: Convert to fraction form
    3.90/4.20 = 4.20/x
  3. Step 3: Cross multiply
    3.90x = 4.20 × 4.20
  4. Step 4: Simplify right side
    3.90x = 17.68
  5. Step 5: Solve for x
    x = 17.68/3.90
  6. Step 6: Final answer
    x = 4.53

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Why These Related Problems?

These problems maintain the same ratio (1.08) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.