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Finding the Fourth Proportional to 639.60, 959.40 and 206.80

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Solution

The fourth proportional to 639.60, 959.40 and 206.80 is: 310.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.60 : 959.40 = 206.80 : x
  2. Step 2: Convert to fraction form
    639.60/959.40 = 206.80/x
  3. Step 3: Cross multiply
    639.60x = 959.40 × 206.80
  4. Step 4: Simplify right side
    639.60x = 198,403.92
  5. Step 5: Solve for x
    x = 198,403.92/639.60
  6. Step 6: Final answer
    x = 310.20

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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.