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Finding the Fourth Proportional to 428.69, 643.05 and 212.19

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Solution

The fourth proportional to 428.69, 643.05 and 212.19 is: 318.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.69 : 643.05 = 212.19 : x
  2. Step 2: Convert to fraction form
    428.69/643.05 = 212.19/x
  3. Step 3: Cross multiply
    428.69x = 643.05 × 212.19
  4. Step 4: Simplify right side
    428.69x = 136,448.78
  5. Step 5: Solve for x
    x = 136,448.78/428.69
  6. Step 6: Final answer
    x = 318.30

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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.