The digits 1, 2, 3, 4, 5, 6, and 7 are written on separate cards. Three are drawn and placed in order of drawing. In how many ways can numbers greater than 500 be formed?
The numbers 1,2,3,4,5,6,7,8,9 and 10 are written around a circle in arbitrary order. We add all the numbers with their neighbours, we get 10 sums that way. What is the maximum possible value of the smallest of these sums?
it is a known that a particular
machine will make product with
a qualified rate of 90% when it is
running well, but will do so with
a qualified rate of only 30% when
it is not running well. The
probability that machine is
running well is 75% normally .
Suppose that one day the first
product made by the machine is
qualified. Find the probabiliy
that the machine is running well at
this time.