Fill in the blanks to make the statements true:

Two quantities are said to vary ……………. With each other if they increase (decrease) together in such a manner that the ratio of their corresponding values remains constant.

Fill in the blanks to make the statements true:

Both x and y are said to vary ……… with each other if for some positive number k, xy = k.

Fill in the blanks to make the statements true:

x and y are said to vary directly with each other if for some positive number k, ……… = k.

Fill in the blanks to make the statements true:

Two quantities are said to vary ……………. with each other if an increase in one causes a decrease in the other in such a manner that the product of their corresponding values remains constant.