00:03
Now here in this question, we have electronic store, right, which receives the shipment of 20 graphing calculators, right? turns out that eight of them are defective.
00:12
Now, four of the calculators are selected to be sent to a local hash score, right? so you select four out of this 20, right? to be selected to be sent to a local score.
00:23
So the question a is how many selections can be made? well, you take four out of 20 basically, right? so you take four out of 20, of course, that's given by, 20 factor divided by 4 factor rate, right? and 20 minus 4 factor, that's 16 factor, right? so you can work out this by taking the 20 factory and divided by 4 factor, multiplied by 16 factor, and you found this to be given by 4, 8, 4, 5, right? and b, how many of those selections where contain no defective calculators, right? so you pick up four of them, none of them is going to be defective, right? none of them is going to be defective.
01:12
You know, eight of them is going to be defective, right? so if you want to select, so none of them is defective, of course, you have basically 12 of them, none of them is defective, right? so how many ways you can find from 12 of them select four, right? so that's given by 12 factor divided by 12 factor divided by four factor and eight factor, right? so you can't get this, this will be given by, 12 factor divided by 4 factor times 12 factor...