Solve the following problems (1 - 6)
1.8. How many different four-digit numbers can be written with the help of nine significant figures, neither of which will not be repeated?
2.8. 6 On a shelf radio tubes, two of which are worthless. Randomly selected two radio tubes. What is the probability that they are fit for use?
3.8. Three workers collect bearings. The probability that the bearing is assembled the first working - the highest quality, is 0.7, the second - 0.8, the third - 0.6. To control is taken by one of the bearing collected by each worker. What is the probability that the highest quality will be: a) All the bearings; b) two bearings; c) at least one bearing?
4.8. The display class has 10 personal computers and 15 of the first type of the second type. The possibility that during the work on the first type of computer failure occurs, is 0.9 and the computer of the second type - 0.7. Find the probability that: a) on a randomly selected computer during work not will fail; b) computer, while working on which no failure occurred, - the first type.
5.8. With mass production of semiconductor diodes probability of marriage during molding is 0.1. Find the probability that eight diodes scanned OTC is defective: a) two; b) not less than two; c) no more than two.
6.8. The average number of cars arriving at the fleet for 1 min, is equal to two. Find the probability that 5 minutes to arrive at least two cars, if the cars arrival elementary stream.