Marco is making three tiles pictures. he uses 310 green tiles to make each picture. he uses 50 fewer red tiles than green tiles for each picture. how many red and green tiles does he use in all?

The coverage of a base station of a telecommunication company forms a disk with a radius of (kilometers). let be the distance of a cellphone from a base station. assume that the location of cellphones in use are randomly uniformly distributed within the disk. calculate the mean and variance for the random variable.