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Finding the Fourth Proportional to 428.45, 642.79 and 120.31

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Solution

The fourth proportional to 428.45, 642.79 and 120.31 is: 180.49

Step by Step Solution

  1. Step 1: Write the proportion equation
    428.45 : 642.79 = 120.31 : x
  2. Step 2: Convert to fraction form
    428.45/642.79 = 120.31/x
  3. Step 3: Cross multiply
    428.45x = 642.79 × 120.31
  4. Step 4: Simplify right side
    428.45x = 77,332.89
  5. Step 5: Solve for x
    x = 77,332.89/428.45
  6. Step 6: Final answer
    x = 180.49

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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.