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Finding the Third Proportional to 1,989 and 3,929

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Solution

The third proportional to 1,989 and 3,929 is: 7,761.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,989 : 3,929 = 3,929 : x
  2. Step 2: Convert to fraction form
    1,989/3,929 = 3,929/x
  3. Step 3: Cross multiply
    1,989x = 3,929 × 3,929
  4. Step 4: Simplify right side
    1,989x = 15,437,041
  5. Step 5: Solve for x
    x = 15,437,041/1,989
  6. Step 6: Final answer
    x = 7,761.21

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Why These Related Problems?

These problems maintain the same ratio (1.98) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.