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Finding the Fourth Proportional to 639.80, 959.70 and 445.40

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Solution

The fourth proportional to 639.80, 959.70 and 445.40 is: 668.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.80 : 959.70 = 445.40 : x
  2. Step 2: Convert to fraction form
    639.80/959.70 = 445.40/x
  3. Step 3: Cross multiply
    639.80x = 959.70 × 445.40
  4. Step 4: Simplify right side
    639.80x = 427,450.38
  5. Step 5: Solve for x
    x = 427,450.38/639.80
  6. Step 6: Final answer
    x = 668.10

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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.