Frank walks at a speed of 3 miles per hour. Aaron walks at a speed of 4 miles per hour. If
Frank starts walking 3 hours before Aaron, how
long does it take Aaron to catch up to him?

(a) calculate the molarity of a solution that contains 0.0345 mol nh4cl in 400 ml of solution. (b) how many moles of hno3 are present in 35.0 ml of a 2.20 m solution of nitric acid? (c) how many milliliters of 1.50 m koh solution are needed to supply 0.125 mil of koh ?

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?

Determine the number of girls in a math class with 87 boys if there are 25 girls for every 75 boys