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Finding the Fourth Proportional to 428.58, 642.87 and 120.42

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Solution

The fourth proportional to 428.58, 642.87 and 120.42 is: 180.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.58 : 642.87 = 120.42 : x
  2. Step 2: Convert to fraction form
    428.58/642.87 = 120.42/x
  3. Step 3: Cross multiply
    428.58x = 642.87 × 120.42
  4. Step 4: Simplify right side
    428.58x = 77,414.41
  5. Step 5: Solve for x
    x = 77,414.41/428.58
  6. Step 6: Final answer
    x = 180.63

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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.