A quantity a varies inversely as a quantity b, if, when b changes, a changes in the inverse ratio. What happens to the quantity a if the quantity b doubles? (site 1)

Let us write the inverse variation in the given in an equation form,

a = k / b

where k is the constant of proportion.

If the value of b is double, there should be a corresponding change in a.

(x) (a) = k / 2b

(x) (a) = (1/2) (k/b)

The value of x is 1/2. Therefore, the value of a is halved.