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Finding the Third Proportional to 7,780 and 9,990

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Solution

The third proportional to 7,780 and 9,990 is: 12,827.78

Step by Step Solution

  1. Step 1: Write the proportion equation
    7,780 : 9,990 = 9,990 : x
  2. Step 2: Convert to fraction form
    7,780/9,990 = 9,990/x
  3. Step 3: Cross multiply
    7,780x = 9,990 × 9,990
  4. Step 4: Simplify right side
    7,780x = 99,800,100
  5. Step 5: Solve for x
    x = 99,800,100/7,780
  6. Step 6: Final answer
    x = 12,827.78

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Why These Related Problems?

These problems maintain the same ratio (1.28) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.