An electronics store receives a shipment of 30 graphing calculators, including 3 that are defective. Four of the calculators are selected to be sent to a local high school.
A. How many selections can be made using the original shipment?
B. How many of these selections will contain no defective calculators?
A. How many selections can be made using the original shipment?
B. How many of these selections will contain no defective calculators?
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Selecting 30 out of 4, when order doesn't matter, that means 30C4, or C(30,4) or combination (30, 4), i.e.
30! / (4! (30-4)!) = 30x29x28x27 / (4x3x2x1)
To get no defective calculators, it means you need to select all 4 from the set of 27 good calculators, i,e, C(27,4)
30! / (4! (30-4)!) = 30x29x28x27 / (4x3x2x1)
To get no defective calculators, it means you need to select all 4 from the set of 27 good calculators, i,e, C(27,4)