25000× 40 = 100000 square meters = 100 hectares = 1 square kilometer.
Area conversion
1 cm2 = 100 mm2 =0. 1550 in2.
1 square meter = 10000 square centimeter = 1. 1960 square yard.
1 hectare =15mu =10000m2.
1 mu =666.67 square meters.
1 ha =10000m2 = 2.475438+0 1 mu.
1 km2 =100ha = 0.38 1 km2.
Hectares, metric land units. Nickname: square meter, square hectare (easy to remember and convert). The hectare is the metric unit (international unit) of area. A piece of land with an area of one hectare is 10000 square meters.
How to improve mathematical thinking;
1, starting from actual demand.
For example, family members go shopping, which way can they get to their destination faster, and what methods can they use to save money. These real lives are very helpful for children to think and understand, and often mathematical thinking is formed unconsciously.
2. Start with a breakthrough.
For example, equations, solving a problem is very complicated, and using equations will be very simple. When you encounter some problems, you will always need to find a breakthrough, such as reverse thinking and comparative thinking. The process of these breakthroughs is itself a mathematical thinking.
3, starting from the actual case.
There are many practical typical cases, which are all in our textbooks. Using these cases, we can see how these books are analyzed. Even if children can't do it by themselves, recitation itself is beneficial. Unfortunately, many people just say that they have nothing to do, and it is getting worse and worse.
multiply operation
1, the same sign is positive, the different sign is negative, and the absolute value is multiplied.
Any number multiplied by zero will get zero.
3. Multiply several numbers that are not equal to zero. The sign of the product is determined by the number of negative factors. When there are odd negative factors, the product is negative, and when there are even negative factors, the product is positive.
When several numbers are multiplied, if one factor is zero, the product is zero.
5. Multiply several numbers that are not equal to zero, first determine the sign of the product, and then multiply it by the absolute value.