ex4.py

cars = 100
space_in_a_car = 4
drivers = 30
passengers = 90
cars_not_driven = cars - drivers
cars_driven = drivers
carpool_capacity = cars_driven * space_in_a_car
average_passengers_per_car = passengers / cars_driven

print "There are" , cars, "cars available."
print "There are only", drivers, "drivers available."
print "There will be", cars_not_driven, "empty cars today."
print "We can transport", carpool_capacity, "people today."
print "We have", passengers, "to carpool today." 
print "We need to put about", average_passengers_per_car, "in each car."

#note about Study drill
# the reason there is an error because of the variable 'passenger' 
# has not been defined 

# if you use 4 for space_in_a_car the result is 120 (not floating point)