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Finding the Fourth Proportional to 428.87, 643.34 and 120.72

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Solution

The fourth proportional to 428.87, 643.34 and 120.72 is: 181.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.87 : 643.34 = 120.72 : x
  2. Step 2: Convert to fraction form
    428.87/643.34 = 120.72/x
  3. Step 3: Cross multiply
    428.87x = 643.34 × 120.72
  4. Step 4: Simplify right side
    428.87x = 77,664.00
  5. Step 5: Solve for x
    x = 77,664.00/428.87
  6. Step 6: Final answer
    x = 181.09

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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.