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Finding the Third Proportional to 999 and 1,290

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Solution

The third proportional to 999 and 1,290 is: 1,665.77

Step by Step Solution

  1. Step 1: Write the proportion equation
    999 : 1,290 = 1,290 : x
  2. Step 2: Convert to fraction form
    999/1,290 = 1,290/x
  3. Step 3: Cross multiply
    999x = 1,290 × 1,290
  4. Step 4: Simplify right side
    999x = 1,664,100
  5. Step 5: Solve for x
    x = 1,664,100/999
  6. Step 6: Final answer
    x = 1,665.77

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Why These Related Problems?

These problems maintain the same ratio (1.29) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.