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Finding the Fourth Proportional to 808.78, 1,115.94 and 643.54

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Solution

The fourth proportional to 808.78, 1,115.94 and 643.54 is: 887.94

Step by Step Solution

  1. Step 1: Write the proportion equation
    808.78 : 1,115.94 = 643.54 : x
  2. Step 2: Convert to fraction form
    808.78/1,115.94 = 643.54/x
  3. Step 3: Cross multiply
    808.78x = 1,115.94 × 643.54
  4. Step 4: Simplify right side
    808.78x = 718,152.03
  5. Step 5: Solve for x
    x = 718,152.03/808.78
  6. Step 6: Final answer
    x = 887.94

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.