1. The survival rate of planting trees is certain, and the planted trees are directly proportional to the surviving trees (right). 2. The area and radius of a circle are proportional (wrong). The circumference of a square is in direct proportion to the length of its side. 4. The height of a cylinder is fixed, and the radius of its bottom surface is proportional to its volume (error). Xiaoming's age is directly proportional to her mother's age. 6. Cone. Well, there are some formulas in which division is proportional and multiplication is inversely proportional. Remember this first, if you know the distance, time and speed will be inversely proportional. Reason: Time × speed = distance (certain) Knowing that time, distance and speed are directly proportional. Reason: distance/speed = time (certain) Knowing speed, distance and time are still proportional.