Answer:
(a) Time t = 16.46 sec
(b) Time t =13.466 sec
(c) Deceleration = 
Explanation:
(a) As the train starts from rest its initial velocity u = 0 m/sec
Acceleration 
Final speed v = 80 km/hr

From first equation of motion v =u+at
So 
(b) Now initial speed u = 22.22 m/sec
As finally train comes to rest so final speed v=0 m/sec
Deceleration 
So 
(c) We have given that initial velocity = 80 km/hr = 22.22 m/sec
Final velocity v = 0 m/sec
Time t = 8.30 sec
So acceleration is given by

As acceleration is negative so it is a deceleration
Roughly 13.8 billion years old according to science
Question
What is the length of the pipe?
Answer:
(a) 0.52m
(b) f2=640 Hz and f3=960 Hz
(c) 352.9 Hz
Explanation:
For an open pipe, the velocity is given by

Making L the subject then

Where f is the frequency, L is the length, n is harmonic number, v is velocity
Substituting 1 for n, 320 Hz for f and 331 m/s for v then

(b)
The next two harmonics is given by
f2=2fi
f3=3fi
f2=3*320=640 Hz
f3=3*320=960 Hz
Alternatively,
and 

(c)
When v=367 m/s then

Personally, I agree with your answer, namely that the likely-intended event happening here is one of acceleration. Having said that, I also want to add: it pains me to see this type of wording because, clearly, it is vague and only invites confusion of the type you are talking about.
Good luck!
The independent variable would be the cleaning products.
The independent variable is the variable that you can manipulate. The change in the independent variable is not affected by other variables. So in this case, the independent variable would be the cleaning product because you will be changing it.