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Finding the Fourth Proportional to 428.80, 643.62 and 418.78

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Solution

The fourth proportional to 428.80, 643.62 and 418.78 is: 628.58

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.80 : 643.62 = 418.78 : x
  2. Step 2: Convert to fraction form
    428.80/643.62 = 418.78/x
  3. Step 3: Cross multiply
    428.80x = 643.62 × 418.78
  4. Step 4: Simplify right side
    428.80x = 269,535.18
  5. Step 5: Solve for x
    x = 269,535.18/428.80
  6. Step 6: Final answer
    x = 628.58

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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.