Question

In a shipment of 22 smartphones, 2 are defective. How many ways can a quality control inspector randomly test 4 smartphones, of which 2 are defective?

Answer 1

Answer:

Therefore the required ways are =190

Step-by-step explanation:

Combination: Combination is the number of selection of items from a collection of items where the order of selection does not matter.

Total number of smartphones =22

Defective phone = 2

Non defective phone = (22-2) =20

The control inspector randomly test 4 smartphones of which 2 are defective.

Non defective phone = 2

The ways to select 2 non defective phone is

$^{20}C_2=\frac{20!}{2!(20-2)!} =\frac{20!}{2!18!}=\frac{19\times 20}{2} =190$

The ways to select 2 defective phone is= $^2C_2=1$

Therefore the required ways are = (190×1) =190