62+ 15=; 54- 13=; 6+ 13=; 84+3+7=; 68-39=; 86+4+6=; 77-48=; 17+ 17=; 46+23+ 17=; 84- 19=; 18+20=; 22+45+ 15=; 6 1-23=; 65+28=; 19+55- 15=; 13+69=; 92-38=; 77+24- 18=; 53+ 18=; 28+ 15-29=; 54+49-38=; 89+ 1 1-2 1=; ?
55+20=; 23+25+ 15=; 76+ 1 1=; 33+26=; 8 1+ 15+5=; 12+26=; 72- 19=; 28+ 18+2=; 68+ 12=; 17+63-33=; 27+ 17=; 72+ 17+3=; 88-62=; 85-68=;
89+ 17-38=; 46+ 19=; 9 1-2=; 17+63-33=; 92-46=; 82-79=; 85+ 17-38=; 55+25=; 67+25=; 83+ 14+6=; 82-73=; 83-47=; 43+29+ 1 1=; 18+36=; 28+39=。
Mixed operation skills of addition and subtraction in second grade mathematics
1, starting with the simplest formula. Mixed operations are divided into different types, and the simplest one is the operation with fraction in the formula. At first, we can find the rules and formulas of mixed operation. After remembering different algorithms and formulas, do addition and subtraction within the specified time. Always train the flexible application of addition and subtraction, pay attention to finding key sentences and clarify the operation order.
2. Pay attention to the operation sequence of addition and subtraction mixed operations, that is, from high to low. If there are brackets, count them first. You can calculate the part that can be reduced first, and then add and subtract. For the mixed operation of addition and subtraction, we should pay attention not to put the numbers that can be combined together, observe the characteristics of the data clearly and find a simple algorithm.
3. Learn to observe and analyze the characteristics between numbers and use formulas appropriately. When adding and subtracting mixed operations, we should first determine the starting point and direction of the operation. Generally, the operation process is determined from the high priority according to the characteristics and operation order between numbers. At the same time, pay attention to the flexible use of operation formulas, such as addition and combination laws, which can make some step-by-step calculation problems simple, and multiplication and distribution laws can make special data participate in the operation.
4. Do more exercises. Practice makes perfect, and doing more exercises is very important for mastering the skills of mixed operation. You can find some representative topics to practice more, get familiar with various types of topics, and find the rules and methods of solving problems.
5. Pay attention to thinking training. In addition to the number of exercises, we should also pay attention to thinking training. Pay attention to thinking and analysis when solving problems, find the characteristics and laws between numbers, and find simple algorithms. Don't blindly pursue speed, pay attention to the accuracy of solving problems.
6. Cultivate good study habits. When doing mixed addition and subtraction, we should pay attention to the habit of careful examination, careful calculation, neat handwriting, correct inspection and timely correction. These habits are very important for improving the accuracy and efficiency of solving problems.