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Finding the Fourth Proportional to 428.70, 643.05 and 120.60

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Solution

The fourth proportional to 428.70, 643.05 and 120.60 is: 180.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.70 : 643.05 = 120.60 : x
  2. Step 2: Convert to fraction form
    428.70/643.05 = 120.60/x
  3. Step 3: Cross multiply
    428.70x = 643.05 × 120.60
  4. Step 4: Simplify right side
    428.70x = 77,551.83
  5. Step 5: Solve for x
    x = 77,551.83/428.70
  6. Step 6: Final answer
    x = 180.90

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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.