Need some help

Hi!
I'm taking a course that requires some programming background, but I'm a complete novice in the field.

when asked to generate a list of 20 uniform random numbers, is it alright if I put in >randu, and just copy-paste the first 20 numbers?? Or is there, as I suspect, a better way of calling out exactly 20 uniform random numbers??

I'm also unable to solve the following problem:
We know that on average 30% of the customers who enter a store make a purchase. Suppose 200
people enter the store today. Run a simulation to see how many purchases we will have today.


Any help is greatly appreciated. i went through the Rmanual, but felt that it did not lend me the information i needed to solve the above queries.
Thanks again