A complex electronic system is built with a certain number of backup components in its subsystems. One subsystem has eight identical components, each with a probability of 0.1 of failing in less than 1,000 hours. The sub system will operate if any four of the eight components are operating. Assume that the components operate independently. Find the probability that a. exactly two of the four components last longer than 1000 hours.
b. the subsystem operates longer than 1000 hours.

The equation x2 – 1x – 90 = 0 has solutions {a, b}. what is a + b?

You drop a rubber ball off the roof of a 50 meter high building onto a paved parking lot. it bounces back up with every bounce, but not quite all the way back up to you. after the first bounce it bounces back only 80 percent of the distance it was dropped from. the pattern continues, meaning after every bounce it comes up to just 80 percent of the previous maximum height. so if before the first bounce the height is 50 meters, what height does the ball reach after the fifth bounce? round your answer to one decimal place and chose the correct response from the choices below:

Acircle has a radius of 5/6 units and is centered at (3.6, 7.8) write the equation of this circle