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Finding the Fourth Proportional to 427.78, 641.86 and 391.32

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Solution

The fourth proportional to 427.78, 641.86 and 391.32 is: 587.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    427.78 : 641.86 = 391.32 : x
  2. Step 2: Convert to fraction form
    427.78/641.86 = 391.32/x
  3. Step 3: Cross multiply
    427.78x = 641.86 × 391.32
  4. Step 4: Simplify right side
    427.78x = 251,172.66
  5. Step 5: Solve for x
    x = 251,172.66/427.78
  6. Step 6: Final answer
    x = 587.15

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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.