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Finding the Fourth Proportional to 428.66, 643.20 and 212.19

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Solution

The fourth proportional to 428.66, 643.20 and 212.19 is: 318.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.66 : 643.20 = 212.19 : x
  2. Step 2: Convert to fraction form
    428.66/643.20 = 212.19/x
  3. Step 3: Cross multiply
    428.66x = 643.20 × 212.19
  4. Step 4: Simplify right side
    428.66x = 136,479.55
  5. Step 5: Solve for x
    x = 136,479.55/428.66
  6. Step 6: Final answer
    x = 318.39

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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.