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Finding the Fourth Proportional to 428.92, 643.41 and 120.78

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Solution

The fourth proportional to 428.92, 643.41 and 120.78 is: 181.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.92 : 643.41 = 120.78 : x
  2. Step 2: Convert to fraction form
    428.92/643.41 = 120.78/x
  3. Step 3: Cross multiply
    428.92x = 643.41 × 120.78
  4. Step 4: Simplify right side
    428.92x = 77,711.06
  5. Step 5: Solve for x
    x = 77,711.06/428.92
  6. Step 6: Final answer
    x = 181.18

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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.