What are some other ways to sanity check your final answer?
It terms of revenue per year, one way is to divide the total revenue by the population to see if its reasonable that everyone would spend X on Y in that year. e.g. £300m buscuit market means everyone in the UK (approx. 60m) spending £5 on biscuits per.
First what are some other ways to check this and second what are some ways to check when its less obvious what to do e.g. for the following questions:
1) How many vet clinics are there in the UK?
2) How many steps did you take to walk here?
Thanks