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Finding the Fourth Proportional to 782.13, 1,078.47 and 639.90

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Solution

The fourth proportional to 782.13, 1,078.47 and 639.90 is: 882.35

Step by Step Solution

  1. Step 1: Write the proportion equation
    782.13 : 1,078.47 = 639.90 : x
  2. Step 2: Convert to fraction form
    782.13/1,078.47 = 639.90/x
  3. Step 3: Cross multiply
    782.13x = 1,078.47 × 639.90
  4. Step 4: Simplify right side
    782.13x = 690,112.95
  5. Step 5: Solve for x
    x = 690,112.95/782.13
  6. Step 6: Final answer
    x = 882.35

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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.