The cost, in millions of dollars, for a company to manufacture x thousand speed boats is given by the function

c(x) = 3x2 - 30x + 225.

find the number of speedboats that must be produced to minimize the cost.

Some boys and girls were asked if they had a pet. one third of the group were boys. there were 20 boys. 20% of the girls had a pet. boys with a pet : girls with a pet = 1 : 5 i need to know how many girls there are.