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Finding the Fourth Proportional to 639.94, 883.20 and 391.21

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Solution

The fourth proportional to 639.94, 883.20 and 391.21 is: 539.92

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.94 : 883.20 = 391.21 : x
  2. Step 2: Convert to fraction form
    639.94/883.20 = 391.21/x
  3. Step 3: Cross multiply
    639.94x = 883.20 × 391.21
  4. Step 4: Simplify right side
    639.94x = 345,516.67
  5. Step 5: Solve for x
    x = 345,516.67/639.94
  6. Step 6: Final answer
    x = 539.92

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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.