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Finding the Fourth Proportional to 685.42, 945.78 and 405.55

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Solution

The fourth proportional to 685.42, 945.78 and 405.55 is: 559.60

Step by Step Solution

  1. Step 1: Write the proportion equation
    685.42 : 945.78 = 405.55 : x
  2. Step 2: Convert to fraction form
    685.42/945.78 = 405.55/x
  3. Step 3: Cross multiply
    685.42x = 945.78 × 405.55
  4. Step 4: Simplify right side
    685.42x = 383,561.08
  5. Step 5: Solve for x
    x = 383,561.08/685.42
  6. Step 6: Final answer
    x = 559.60

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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.