SOLUTION: A sample of 4 telephones is selected from a shipment of 20 phones. There are 5 defective telephones in the shipment. How many of the samples of 4 phones do not include any of the

Question 622155: A sample of 4 telephones is selected from a shipment of 20 phones. There are 5 defective telephones in the shipment. How many of the samples of 4 phones do not include any of the defective ones?
Answer by math-vortex(648) (Show Source): You can put this solution on YOUR website!
Hi, there--
.
This is a combinations problem. We want to choose samples with four non-defective phones and zero defective phones. In the shipment of 20 phones, five are defective. That means that 15 phones are non-defective.
.
The total number of ways to choose four good non-defective phones is 15-choose-4, or 15C4.
.
15C4 = 15! / (4! 11!)
15C4 = (15*14*13*12*11!) / (4*3*2*1*11!)
15C4 =1365
.
There 1,365 ways to choose four working phones from the shipment.
.
Hope this helps!
.
Ms.Figgy
math.in.the.vortex@gmail.com
RELATED QUESTIONS
In a shipment of 20 smart phones, 2 are defective. How many ways can a quality control... (answered by richard1234)

⦁ A truck has a shipment of 300 I-phones. If there are 4 defective I-phones on the (answered by ewatrrr)

A shipment of 20 computer keyboards is rejected if 5 are checked for defects and at least (answered by Boreal)

In a shipment of 18 smart phones, 2 are defective. How many ways can a quality control... (answered by jim_thompson5910)

A factory received a shipment of 16 sprockets, and the vendor who sold the items knows... (answered by ikleyn)

A factory received a shipment of 33 sprockets, and the vendor who sold the items knows... (answered by ikleyn)

From a shipment of 60 transistors, 4 of which are defective, a sample of 4 transistors is (answered by edjones)

#10 From a shipment of 65 transistors, 3 of which are defective, a sample of 4... (answered by ikleyn)

A quality control inspector found that 1.2% of 2500 telephones inspected were defective.... (answered by richwmiller)