John is a door-to-door salesman.  He visits 50 houses a day.  20% of them buy something from them.  Of those that buy something half buy a $50 set of knives and the other half buy a $150 set of knives.  How much does he sell a week when he works 5 days a week?
There are 50*.2=<T>multiply(50, 0.2)=10.0 houses buying from him per day
Of those 10/2=<T>divide(10, 2)=5.0 buy each type of knife set
So he gets 5*50=$<T>multiply(5, 50)=250 per day from the cheap set
He also gets 5*150=$<T>multiply(5, 150)=750 from the expensive set
So he makes a total of 250+750=$<T>add(250, 750)=1000 per day
That means he makes 1000*5=$<T>multiply(1000, 5)=5000
