Please, when you present a list of numbers, such as 4, 8, 16, ..., separate them with commas or semicolons: 4, 8, 16, ...
If x^2 + y^2 = 16, then 16 represents r^2, and r = 4. r cannot be negative in this type of problem.
325*89.1
Let's decompose this into:
325 = 300 + 25
89.1 = 80 + 9 + 0.1
Then we have the multiplication:
(300 + 25)*(80 + 9 + 0.1)
Let's distribute the multiplication:
300*80 + 300*9 + 300*0.1 + 25*80 + 25*9 + 25*0.1
So now we have 6 multiplications that are a lot easier to solve than the initial one that we had.
Then the list of six multiplications involved in solving this problem are:
300*80 = 24,400
300*9 = 2,700
300*0.1 = 30
25*80 = 2,000
25*9 = 225
25*0.1 = 2.5
Now we add all of those and get:
325*89.1 = 24,400 + 2,700 + 30 + 2,000 + 225 + 2.5 = 28,957.5
For C at 7pm they sold most and at 6 am they sold less