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Finding the Third Proportional to 1,821 and 3,990

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Solution

The third proportional to 1,821 and 3,990 is: 8,742.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,821 : 3,990 = 3,990 : x
  2. Step 2: Convert to fraction form
    1,821/3,990 = 3,990/x
  3. Step 3: Cross multiply
    1,821x = 3,990 × 3,990
  4. Step 4: Simplify right side
    1,821x = 15,920,100
  5. Step 5: Solve for x
    x = 15,920,100/1,821
  6. Step 6: Final answer
    x = 8,742.50

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Why These Related Problems?

These problems maintain the same ratio (2.19) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.