A standard Versa-lok block used in residential and commercial retaining wall systems has mean weight 37.19 kg.8 Assume the standard deviation is 0.8 kg and the distribution is approximately normal. A standard block unit is selected at random.
a. What is the probability that the block weighs more than 38 kg? Write a Solution Trail for this problem.
b. What is the probability that the block weighs between 36 and 37 kg?
c. If the block weighs less than 35.5 kg, it cannot be used in certain commercial construction projects. What is the probability that the block cannot be used?
Movie trailers are designed to entice audiences by showing scenes from coming attractions. Several trailers are usually shown in a theater before the start of the main feature, and most are available via the Internet. The duration of a movie trailer is approximately normal, with mean 150 seconds and standard deviation 30 seconds.
a. What is the probability that a randomly selected trailer lasts less than 1 minute?
b. Find the probability that a randomly selected trailer lasts between 2 minutes and 3 minutes 15 seconds.
c. Any movie trailer that lasts beyond 4 minutes and 30 seconds is considered too long. What proportion of movie trailers is too long?
d. Find a symmetric interval about the mean such that 99% of all movie trailer durations lie in this interval.