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Finding the Fourth Proportional to 685.80, 1,028.86 and 198.90

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Solution

The fourth proportional to 685.80, 1,028.86 and 198.90 is: 298.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    685.80 : 1,028.86 = 198.90 : x
  2. Step 2: Convert to fraction form
    685.80/1,028.86 = 198.90/x
  3. Step 3: Cross multiply
    685.80x = 1,028.86 × 198.90
  4. Step 4: Simplify right side
    685.80x = 204,640.25
  5. Step 5: Solve for x
    x = 204,640.25/685.80
  6. Step 6: Final answer
    x = 298.40

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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.