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Finding the Third Proportional to 990 and 2,139.75

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Solution

The third proportional to 990 and 2,139.75 is: 4,624.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    990 : 2,139.75 = 2,139.75 : x
  2. Step 2: Convert to fraction form
    990/2,139.75 = 2,139.75/x
  3. Step 3: Cross multiply
    990x = 2,139.75 × 2,139.75
  4. Step 4: Simplify right side
    990x = 4,578,530.06
  5. Step 5: Solve for x
    x = 4,578,530.06/990
  6. Step 6: Final answer
    x = 4,624.78

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Why These Related Problems?

These problems maintain the same ratio (2.16) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.