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Finding the Fourth Proportional to 685.40, 1,028.39 and 392.85

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Solution

The fourth proportional to 685.40, 1,028.39 and 392.85 is: 589.44

Step by Step Solution

  1. Step 1: Write the proportion equation
    685.40 : 1,028.39 = 392.85 : x
  2. Step 2: Convert to fraction form
    685.40/1,028.39 = 392.85/x
  3. Step 3: Cross multiply
    685.40x = 1,028.39 × 392.85
  4. Step 4: Simplify right side
    685.40x = 404,001.05
  5. Step 5: Solve for x
    x = 404,001.05/685.40
  6. Step 6: Final answer
    x = 589.44

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1.5x scale

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.