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Finding the Fourth Proportional to 639.90, 959.85 and 315.90

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Solution

The fourth proportional to 639.90, 959.85 and 315.90 is: 473.85

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.90 : 959.85 = 315.90 : x
  2. Step 2: Convert to fraction form
    639.90/959.85 = 315.90/x
  3. Step 3: Cross multiply
    639.90x = 959.85 × 315.90
  4. Step 4: Simplify right side
    639.90x = 303,216.62
  5. Step 5: Solve for x
    x = 303,216.62/639.90
  6. Step 6: Final answer
    x = 473.85

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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.