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Finding the Fourth Proportional to 428.94, 643.59 and 212.76

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Solution

The fourth proportional to 428.94, 643.59 and 212.76 is: 319.23

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.94 : 643.59 = 212.76 : x
  2. Step 2: Convert to fraction form
    428.94/643.59 = 212.76/x
  3. Step 3: Cross multiply
    428.94x = 643.59 × 212.76
  4. Step 4: Simplify right side
    428.94x = 136,930.21
  5. Step 5: Solve for x
    x = 136,930.21/428.94
  6. Step 6: Final answer
    x = 319.23

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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.