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Finding the Fourth Proportional to 988.31, 1,363.87 and 639

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Solution

The fourth proportional to 988.31, 1,363.87 and 639 is: 881.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    988.31 : 1,363.87 = 639 : x
  2. Step 2: Convert to fraction form
    988.31/1,363.87 = 639/x
  3. Step 3: Cross multiply
    988.31x = 1,363.87 × 639
  4. Step 4: Simplify right side
    988.31x = 871,513.73
  5. Step 5: Solve for x
    x = 871,513.73/988.31
  6. Step 6: Final answer
    x = 881.82

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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.