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Finding the Fourth Proportional to 853.65, 1,279.43 and 390.78

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Solution

The fourth proportional to 853.65, 1,279.43 and 390.78 is: 585.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    853.65 : 1,279.43 = 390.78 : x
  2. Step 2: Convert to fraction form
    853.65/1,279.43 = 390.78/x
  3. Step 3: Cross multiply
    853.65x = 1,279.43 × 390.78
  4. Step 4: Simplify right side
    853.65x = 499,975.66
  5. Step 5: Solve for x
    x = 499,975.66/853.65
  6. Step 6: Final answer
    x = 585.69

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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.