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Finding the Fourth Proportional to 855.56, 1,278.45 and 643.11

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Solution

The fourth proportional to 855.56, 1,278.45 and 643.11 is: 960.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    855.56 : 1,278.45 = 643.11 : x
  2. Step 2: Convert to fraction form
    855.56/1,278.45 = 643.11/x
  3. Step 3: Cross multiply
    855.56x = 1,278.45 × 643.11
  4. Step 4: Simplify right side
    855.56x = 822,183.99
  5. Step 5: Solve for x
    x = 822,183.99/855.56
  6. Step 6: Final answer
    x = 960.98

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.