Fill in the blanks in each of the following so as to make the statement true: Two quantities are said to vary. with each other if they increase (decrease) together in such a way that the ratio of the corresponding values remains same. `x\ a n d\ y` are said to vary directly with each other if for some positive number `k ,\ \ \ dot=kdot` If `u\ =3\ v ,` then u and `v` vary . with each other.