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Finding the Fourth Proportional to 643.26, 887.76 and 391.20

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Solution

The fourth proportional to 643.26, 887.76 and 391.20 is: 539.89

Step by Step Solution

  1. Step 1: Write the proportion equation
    643.26 : 887.76 = 391.20 : x
  2. Step 2: Convert to fraction form
    643.26/887.76 = 391.20/x
  3. Step 3: Cross multiply
    643.26x = 887.76 × 391.20
  4. Step 4: Simplify right side
    643.26x = 347,291.71
  5. Step 5: Solve for x
    x = 347,291.71/643.26
  6. Step 6: Final answer
    x = 539.89

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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.