# 1 significant digit but the answer doesn't make sense

john merrick
Homework Statement:
A train on a straight track sounds a 400 Hz horn when passing a parked car on
the road. The train is moving at 20 m/s and the temperature is 10°C. Find the
apparent frequency of the horn for a person sitting inside the car when the train
is approaching and when the train is moving away
Relevant Equations:
no equation
my problem is not how you get the answer... 425.16Hz for approaching. it has to be do the right amount of significant digits.

so it should be 1 significant digit which would mean 400hz. which would make no sense since i started with 400hz.

i'm assuming they should have written the question with a decimal after one of the numbers so you would be looking at 2 or 3 significant digits in your final answer.

Just call it 425Hz, or if you really want 430Hz. I don't think anyone will really care too much about it!

john merrick
i got no problem with that but they are marking on the correct significant digits. so you just can't but whatever you want.