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Finding the Fourth Proportional to 428.91, 643.34 and 120.78

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Solution

The fourth proportional to 428.91, 643.34 and 120.78 is: 181.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.91 : 643.34 = 120.78 : x
  2. Step 2: Convert to fraction form
    428.91/643.34 = 120.78/x
  3. Step 3: Cross multiply
    428.91x = 643.34 × 120.78
  4. Step 4: Simplify right side
    428.91x = 77,702.00
  5. Step 5: Solve for x
    x = 77,702.00/428.91
  6. Step 6: Final answer
    x = 181.16

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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.