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Finding the Fourth Proportional to 427.78, 641.90 and 420.15

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Solution

The fourth proportional to 427.78, 641.90 and 420.15 is: 630.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    427.78 : 641.90 = 420.15 : x
  2. Step 2: Convert to fraction form
    427.78/641.90 = 420.15/x
  3. Step 3: Cross multiply
    427.78x = 641.90 × 420.15
  4. Step 4: Simplify right side
    427.78x = 269,694.29
  5. Step 5: Solve for x
    x = 269,694.29/427.78
  6. Step 6: Final answer
    x = 630.45

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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.