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Finding the Fourth Proportional to 825.80, 1,238.70 and 642.20

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Solution

The fourth proportional to 825.80, 1,238.70 and 642.20 is: 963.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    825.80 : 1,238.70 = 642.20 : x
  2. Step 2: Convert to fraction form
    825.80/1,238.70 = 642.20/x
  3. Step 3: Cross multiply
    825.80x = 1,238.70 × 642.20
  4. Step 4: Simplify right side
    825.80x = 795,493.14
  5. Step 5: Solve for x
    x = 795,493.14/825.80
  6. Step 6: Final answer
    x = 963.30

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.