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Finding the Fourth Proportional to 428.50, 643.98 and 212.22

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Solution

The fourth proportional to 428.50, 643.98 and 212.22 is: 318.94

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.50 : 643.98 = 212.22 : x
  2. Step 2: Convert to fraction form
    428.50/643.98 = 212.22/x
  3. Step 3: Cross multiply
    428.50x = 643.98 × 212.22
  4. Step 4: Simplify right side
    428.50x = 136,665.44
  5. Step 5: Solve for x
    x = 136,665.44/428.50
  6. Step 6: Final answer
    x = 318.94

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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.