Suppose you have a bag with 10 black and 10 red balls, with the balls of each color numbered 1 to 10. Suppose you pick two balls uniformly at random from the bag. a. Show that the probability that you pick a ball of each color is 10/19.
b. Show that the probability that you pick a ball of each color, with the number on the red ball being one less than the number on the black ball, is 9/190.

On a architect's drawing of a house, 1 inche representa 1.5

Afactory makes propeller drive shafts for ships. a quality assurance engineer at the factory needs to estimate the true mean length of the shafts. she randomly selects four drive shafts made at the factory, measures their lengths, and finds their sample mean to be 1000 mm. the lengths are known to follow a normal distribution whose standard deviation is 2 mm. calculate a 95% confidence interval for the true mean length of the shafts. input your answers for the margin of error, lower bound, and upper bound.

I’m stuck on this equation, anyone got the answer?