Let T be the time taken in minutes to see a doctor. The surgery stipulates that no one will have to wait longer than 35 minutes. The probability density function is
given by
f(t)= t/450 ,0≤t≤35
Determine
a) The mean waiting time µ
b) The standard deviation σ
c) The probability that you will see a doctor within 15 minutes.

Ascientist wants to use a model to present the results of his detailed scientific investigation. why would a model be useful? a )because the model makes the concepts easier to understand b) because the model is easy to put together and to use c) because the model prevents other scientists from asking questions d) because the model requires the audience to pay full attention to it i don't know what to choose because between a and d a is much more likely than d because it only wants to get the attention of the audience. i'm confuse.

Bring the fraction a/a-4 to a denominator of 16-a^2

How many kilograms of a 5% salt solution and how many kilograms of a 15% salt solution must be mixed together to make 45kg of an 8% salt solution?