The first question can be solved without any computations.
The question gives us conditions with regard to Time and Distance.
As one should already know, Rate x Time = Distance
Hence if any of the choices give an indication of the Rate we are sorted, since it will provide us with either a Yes or a No answer (which we don't need to work out in order to answer the question).
1) "less than 6.4 km/h" is an indication of Rate (which can of course be converted into mph)
2) "more than 9 minutes per km" is also an indication of Rate (which can be converted into km/h and than into mph)
So D is the answer.
For the third question, reason it this way:
h(100) = (2^50)*(1*2*3*...50)
h(100) is divisible by 2. So h(100)+1 is not divisible by 2, i.e. 2 is not a factor of h(100)+1.
h(100) is divisible by 3. So h(100)+1 is not divisible by 3, i.e. 3 is not a factor of h(100)+1.
h(100) is divisible by 50. So h(100)+1 is not divisible by 50, i.e. 50 is not a factor of h(100)+1.
Hence every prime number upto 50 is not a factor of h(100)+1.
So p > 50.
I disagree with you on number 1. We got the same answer but your logic is flawed IMO..
you say a calculation is not necessary.
We have an inequality not simply and equation with an "=" sign..
what if 1) said less than 9 km/hr?
the trip then could have taken less or more than 2 hours.
or what if from 1) and 2) we got some range of time?
1< time <3