If anyone could answer these I would really appreciate it!!

Distance covered = speed x timethe distance traveled going against the stream = distance traveled with the stream.therefore it is the speed and the time that are the variables.as he travels the same distance both ways, speed x time is the same for each way.going upstream his speed is 4 kph; going downstream his speed is 6 kph.therefore we have two simultaneous equations: time upstream x 4 = time downstream x 6time upstream + time downstream = 60 minutestherefore we have the equation: time upstream = 6/10 hour, time downstream therefore = 4/10 hour.distance traveled at 4km/hr in 6/10 hour = 24/10 = 2.4km.check: distance traveled at 6km/hr in 4/10 hour = 24/10 = 2.4km.

The disturbance in a transverse wave is perpendicular to the wave motion.unlike a transverse wave, the disturbance in a longitudinal wave is parallel to the wave motion (a), that is, back and forth.

Answer would be

All these statements are related to drake's equation. it is a probabilistic equation that shows an aproximate number of civilizations in our galaxy that we can communicate with. all the numbers that are inserted into equation are not precisely known so the result varies from 1000 to 100,000,000. the equations was not created to calculate exact number of extraterrestrial civilizations but to increase scientific knowledge how to find them.the equation is: where: n=  represents the number of civilizations in our galaxy that we could in principle communicate with today.  the average rate of  star formation  in  our galaxy  the fraction of those stars that have  planets  represents the number of planets in the galaxy that are in principle capable of having surface liquid water and life.  essentially represents the probability that life eventually arises on a habitable planet.  represents the number of life-bearing planets in the galaxy.  epresents the total number of planets on which intelligent beings have evolved and developed a communicating civilization at some time in the galaxy's history.    essentially represents the probability that on a planet with life, some organisms will eventually evolve to the point where they can build radio telescopes.    is a factor that depends on how long civilizations that reach our level of technology are able to survive.