Question

In how many ways can 2 singers be selected from 4 who came to an audition?

A. 6
B. 2
C. 12
D. 4

In a batch of 280 water purifiers, 12 were found to be defective. What is the probability that a water purifier chosen at random will be defective? Write the probability as a percent. Round to the nearest tenth of a percent if necessary.

A. 4.3%
B. 5.6%
C. 95.7%
D. 71.8%

Answer 1

First part its 4C2 = 4*3 / 2 = 6

Second part
12 * 100
---------- = 4.3 %
280

Answer 2

Answer: A. 6

A. 4.3%

Explanation:

The total number of singers = 4

To choose singers = 2

The number of ways to choose 2 singers from 4=
`^4C_2=(4!)/(2!(4-2)!)=3*2=6`

Hence, A is the right option.

The total number of water purifiers T= 280

The number of defective purifiers D= 12

The probability that a water purifier chosen at random will be defective (in percent)=
`\frac{\text{T}}{\text{D}}*100`

`=(12)/(280)*100\\=0.042857*100\\=4.2857\%\approx4.3\%`

Hence, A is the right option.