Working together, it takes two roofers 10 hours to put a new roof on a portable classroom. if the first roofer can do the job by himself in 12 hours, how many hours will it take the second roofer to do the job by himself?

"you know, playing tennis is healthier than watching a tennis match on television," katya remarked to her couch potato brother. in this sentence, healthier is a/an a. superlative. b. comparative. c. positive form. d. adverb.

Rockwell hardness of pins of a certain type is known to have a mean value of 50 and a standard deviation of 1.1. (round your answers to four decimal places.) (a) if the distribution is normal, what is the probability that the sample mean hardness for a random sample of 8 pins is at least 51?

1mile equals approximately 1.6 kilometers. which best approximates the number of miles in 6 kilometers?