A is the value of b multiplied by a constant, so a and b are proportional.

As A increases with B, AB is directly proportional (the bigger A, the bigger B, and the directly proportional AB).

[Edit this paragraph] is inversely proportional.

A is proportional to the reciprocal of B (that is, the reciprocal is multiplied by a constant), so A is inversely proportional to B. ..

When A decreases with the increase of B, AB is inversely proportional (the larger A is, the smaller B is, and AB is inversely proportional).

The relationship between physical quantity y and physical quantity x can be written as:

Y = ax, and a is constant, then y is proportional to X.

Y = a/x, and a is constant, then y is inversely proportional to X.

pay attention to

Here (including textbooks), it is directly proportional, and in a strict mathematical sense, it must be a constant ratio.

[Edit this paragraph] Related examples

(Time) is constant, (distance) is proportional to (speed).

(Speed) is constant, (distance) is proportional to (time).

(Work efficiency) is certain, and (total workload) is directly proportional to (time).

(Time) is constant, and (total workload) is directly proportional to (work efficiency).

(Pressure) is constant, and (pressure) is directly proportional to (stress area).

(Density) is constant, (mass) is directly proportional to (volume).

(Voltage) is constant, (power) is in direct proportion to (current intensity).