An electronics store receives a shipment of 20 graphing calculators, including 3 that are defective. Four of the calculators are selected to be sent to a local high school. A. How many selection can be made using the originial shipment?

Answer 1

If the only distinction between calculators is the defects then there are 4 possible selections, namely
0, 1, 2, 3 defective calculators along with good ones for the balance.

If the calculators bear serial numbers, i.e. they are considered distinct, then there are (20,4)=20!/(4!16!)=4845 selections.

Answer 2

An electronics store receives a shipment of 20 graphing calculators, including 2 that are defective. Four of the calculators are selected to be sent to a local high school. A. How many selection can be made using the originial shipment?

Answer 3

An electronics store receives a shipment of 20 graphing​ calculators, including 4 that are defective. Four of the calculators are selected to be sent to a local high school. How many of these selections will contain no defective​ calculators?