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Finding the Fourth Proportional to 643.36, 887.85 and 391.20

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Solution

The fourth proportional to 643.36, 887.85 and 391.20 is: 539.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    643.36 : 887.85 = 391.20 : x
  2. Step 2: Convert to fraction form
    643.36/887.85 = 391.20/x
  3. Step 3: Cross multiply
    643.36x = 887.85 × 391.20
  4. Step 4: Simplify right side
    643.36x = 347,322.49
  5. Step 5: Solve for x
    x = 347,322.49/643.36
  6. Step 6: Final answer
    x = 539.86

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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.