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Finding the Fourth Proportional to 685.72, 1,028.80 and 393.55

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Solution

The fourth proportional to 685.72, 1,028.80 and 393.55 is: 590.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    685.72 : 1,028.80 = 393.55 : x
  2. Step 2: Convert to fraction form
    685.72/1,028.80 = 393.55/x
  3. Step 3: Cross multiply
    685.72x = 1,028.80 × 393.55
  4. Step 4: Simplify right side
    685.72x = 404,880.71
  5. Step 5: Solve for x
    x = 404,880.71/685.72
  6. Step 6: Final answer
    x = 590.45

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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.