00:01
From the question given we came to know that there are 25 machines, 25 computers in stores among us 20 are new and 5 are refurbished.
00:15
Right? so, now the first channel question is we are selecting 6 computers from this.
00:24
Okay, selecting 6 computers out of which 2 are refurbished.
00:30
That for the probability is equal to run the 25 computers we are selecting big.
00:36
Then out of which two are re -forbished.
00:40
So from 5 computers we are selecting to the remaining 4 we are selecting from 20.
00:45
So 20 c4 multiplied by 5c2 divided by 20 c6.
00:50
Then apply the formula you know very well ncr is equal to factorial n divided by factorial r multiplied by factor 4.
01:00
N minus r so by using this formula we can get it so for the first one 20 factorial divided by 4 factorial multiplied by 16 factorial multiplied by next one is 5 factorial divided by 2 factorial into 3 factorial divided by 25 factorial divided by 6 factorial into 19 factorial so by simplifying this we make the answer as 48 ,450 divided by 8 ,085 ,500 and the answer for this is 0 .055.
01:39
So this is the probability of selecting two refurbished computers, right? then second question, at least two or not refurbished...