A calculator manufacturing company checks 500 calculator units, and 25 of them have non-functioning keys. Approximate the relative frequency of a non-defective unit from this batch of items. Express your answer in the simplest form of a fraction.
• 1/20
• 475/500
• 25/500
• 19/20
1 - 25/500 = 475/500
So, the relative frequency of a non-defective unit from this batch of items is 475/500, which can be simplified to 19/20.
Therefore, the correct answer is 19/20.