Mary bought a smart phone and has $11.43 left. How much did Mary have before she bought the smart phone? Write an equation and solve it by using the information in the table.
Electronics
Sale Price (5)
MP3 Player
$39
Computer
$299
Tablet
$199
Smart Phone
A$78
B$27.57
C$50.43
D$66.57

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.