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Finding the Fourth Proportional to 769.20, 1,153.80 and 639.60

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Solution

The fourth proportional to 769.20, 1,153.80 and 639.60 is: 959.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    769.20 : 1,153.80 = 639.60 : x
  2. Step 2: Convert to fraction form
    769.20/1,153.80 = 639.60/x
  3. Step 3: Cross multiply
    769.20x = 1,153.80 × 639.60
  4. Step 4: Simplify right side
    769.20x = 737,970.48
  5. Step 5: Solve for x
    x = 737,970.48/769.20
  6. Step 6: Final answer
    x = 959.40

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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.