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Finding the Third Proportional to 21,405 and 31,989

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Solution

The third proportional to 21,405 and 31,989 is: 47,806.41

Step by Step Solution

  1. Step 1: Write the proportion equation
    21,405 : 31,989 = 31,989 : x
  2. Step 2: Convert to fraction form
    21,405/31,989 = 31,989/x
  3. Step 3: Cross multiply
    21,405x = 31,989 × 31,989
  4. Step 4: Simplify right side
    21,405x = 1,023,296,121
  5. Step 5: Solve for x
    x = 1,023,296,121/21,405
  6. Step 6: Final answer
    x = 47,806.41

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.