Water waves of wavelength 4m are produced by two generators S1 and S2.
Each generation when operated by itself produces waves which have an amplitude A and P which is 3m from S1 and 5m from S2.
When the generator are operated in phase, what is the amplitude of oscillation at P?
A. 0
B.1/2A
C. A
D.2A

»»answer is A. I just need the reasoning :)

It was crowded with sewer like smells. bad sewer systems

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.