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Finding the Fourth Proportional to 428.74, 643.13 and 209.55

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Solution

The fourth proportional to 428.74, 643.13 and 209.55 is: 314.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.74 : 643.13 = 209.55 : x
  2. Step 2: Convert to fraction form
    428.74/643.13 = 209.55/x
  3. Step 3: Cross multiply
    428.74x = 643.13 × 209.55
  4. Step 4: Simplify right side
    428.74x = 134,767.89
  5. Step 5: Solve for x
    x = 134,767.89/428.74
  6. Step 6: Final answer
    x = 314.34

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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.