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Finding the Fourth Proportional to 2,661, 3,991.32 and 686.40

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Solution

The fourth proportional to 2,661, 3,991.32 and 686.40 is: 1,029.55

Step by Step Solution

  1. Step 1: Write the proportion equation
    2,661 : 3,991.32 = 686.40 : x
  2. Step 2: Convert to fraction form
    2,661/3,991.32 = 686.40/x
  3. Step 3: Cross multiply
    2,661x = 3,991.32 × 686.40
  4. Step 4: Simplify right side
    2,661x = 2,739,642.05
  5. Step 5: Solve for x
    x = 2,739,642.05/2,661
  6. Step 6: Final answer
    x = 1,029.55

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.