Question

An electronics store receives a shipment of 20 graphing calculators, including 3 that aredefective. Four of the calculators are selected to be sent to a local high school. Howmany of these selections will contain no defective calculators?

Answer 1

Given:

Total calculatore = 20

Defective =3

Total non defective calculatore is:

`\begin{gathered} =20-3 \\ =17 \end{gathered}`

For four calculatore:

`\begin{gathered} ^(17)C_4 \\ =(17!)/(4!(17-4)!) \\ =(17*16*15*14*13!)/(13!*4*3*2*1) \\ =2380 \end{gathered}`

So total 2380 selection will contain no defective calculators.