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Finding the Fourth Proportional to 1,380.85, 1,906.79 and 939.80

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Solution

The fourth proportional to 1,380.85, 1,906.79 and 939.80 is: 1,297.76

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,380.85 : 1,906.79 = 939.80 : x
  2. Step 2: Convert to fraction form
    1,380.85/1,906.79 = 939.80/x
  3. Step 3: Cross multiply
    1,380.85x = 1,906.79 × 939.80
  4. Step 4: Simplify right side
    1,380.85x = 1,792,006.60
  5. Step 5: Solve for x
    x = 1,792,006.60/1,380.85
  6. Step 6: Final answer
    x = 1,297.76

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.