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Finding the Fourth Proportional to 428.96, 640.84 and 421.22

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Solution

The fourth proportional to 428.96, 640.84 and 421.22 is: 629.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.96 : 640.84 = 421.22 : x
  2. Step 2: Convert to fraction form
    428.96/640.84 = 421.22/x
  3. Step 3: Cross multiply
    428.96x = 640.84 × 421.22
  4. Step 4: Simplify right side
    428.96x = 269,934.62
  5. Step 5: Solve for x
    x = 269,934.62/428.96
  6. Step 6: Final answer
    x = 629.28

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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.