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Finding the Fourth Proportional to 428.67, 642.90 and 120.55

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Solution

The fourth proportional to 428.67, 642.90 and 120.55 is: 180.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.67 : 642.90 = 120.55 : x
  2. Step 2: Convert to fraction form
    428.67/642.90 = 120.55/x
  3. Step 3: Cross multiply
    428.67x = 642.90 × 120.55
  4. Step 4: Simplify right side
    428.67x = 77,501.90
  5. Step 5: Solve for x
    x = 77,501.90/428.67
  6. Step 6: Final answer
    x = 180.80

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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.