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Finding the Fourth Proportional to 855.78, 1,283.74 and 640.72

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Solution

The fourth proportional to 855.78, 1,283.74 and 640.72 is: 961.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    855.78 : 1,283.74 = 640.72 : x
  2. Step 2: Convert to fraction form
    855.78/1,283.74 = 640.72/x
  3. Step 3: Cross multiply
    855.78x = 1,283.74 × 640.72
  4. Step 4: Simplify right side
    855.78x = 822,517.89
  5. Step 5: Solve for x
    x = 822,517.89/855.78
  6. Step 6: Final answer
    x = 961.13

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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.