Nancy decides to buy 30 panels for her allotment and her garden. The panels need to be treated with wood preservative. Each panel is 1.8 m long and 2 m high. 1 litre tin of wood preservative covers 12 square metres. How many tins will she need?

An automobile assembly line operation has a scheduled mean completion time, μ, of 12 minutes. the standard deviation of completion times is 1.6 minutes. it is claimed that, under new management, the mean completion time has decreased. to test this claim, a random sample of 33 completion times under new management was taken. the sample had a mean of 11.2 minutes. assume that the population is normally distributed. can we support, at the 0.05 level of significance, the claim that the mean completion time has decreased under new management? assume that the standard deviation of completion times has not changed.