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Finding the Fourth Proportional to 853.27, 1,278.87 and 390.40

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Solution

The fourth proportional to 853.27, 1,278.87 and 390.40 is: 585.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    853.27 : 1,278.87 = 390.40 : x
  2. Step 2: Convert to fraction form
    853.27/1,278.87 = 390.40/x
  3. Step 3: Cross multiply
    853.27x = 1,278.87 × 390.40
  4. Step 4: Simplify right side
    853.27x = 499,270.85
  5. Step 5: Solve for x
    x = 499,270.85/853.27
  6. Step 6: Final answer
    x = 585.13

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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.