1. We can calculate the sum of the areas of four circles according to the conditions in the topic. It is known that the radius of a circle is 2 cm. According to the area formula of a circle, S=πr? , you can calculate the area of a circle: s = 3.14× 22 =12.56s = 3.14× 22 =12.56cm2.
2. The number of known circles is four. According to the sum of areas = the area of a circle × the number of circles, the sum of areas of four circles can be calculated:12.56× 4 = 50.2412.56× 4 = 50.24 cm2, so the sum of areas of four circles is 50.24cm2..
A round object.
1, Manufacture and design of circular objects. The manufacture and design of circular objects are relatively simple, because they don't have too many sides and corners, and they can be easily described by geometric formulas. In addition, materials for making circular objects are also easily available. For example, common spheres can be made of various materials such as plastic, rubber and crystal.
2. The application scope of circular objects. Circular objects are widely used in various fields. For example, in the medical field, circular objects are often used in medical equipment, such as CT scanners, nuclear magnetic resonance vibrators and so on. In the mechanical field, circular objects can be used for various bearings, hubs, pipes and so on.
3. The characteristics of circular objects. Circular objects have some unique characteristics. First of all, they have no edges and corners, so they won't scratch hands or other objects. Secondly, circular objects are easy to roll, so a lot of time and energy can be saved in the process of handling and transportation. In addition, circular objects can disperse pressure well, so they are often used as the surfaces of various bearing objects.
4. Circular objects and human culture. Circular objects also play an important role in human culture. For example, in ancient civilizations, circular objects were regarded as mysterious and sacred symbols, such as the sun, the moon and other celestial bodies. In religion, round objects are often used as decorations in altars, statues and other places. In modern culture, circular objects are still widely used, such as medals and badges.