Analysis and solutions
It can be inferred from the final result of 10 during analysis. What should this number be without subtracting 2? How much should it be without dividing by 2? What should it be without multiplying by three? How much should it be without adding 3? In this way, a certain number can be deduced in reverse.
If you don't subtract 2, the number is: 10+2= 12.
If not divided by 2, the number is: 12×2=24.
If not multiplied by 3, the number is: 24÷3=8.
If you don't add 3, the number is: 8-3=5.
Comprehensive formula: (10+2)×2÷3-3=5.
A: The original number was 5.
There are 26 bricks, and the two brothers are competing to choose. The younger brother grabbed the lead and was about to lay bricks when the older brother arrived. My brother saw that my brother picked too much, so he grabbed half of it. The younger brother refused and took half from him. My brother refused to accept it, so he had to give him 5 yuan. At this time, my brother picked two more pieces than his brother. How many pieces was my brother going to choose at first?
Analysis and solutions
First, calculate the final chess pieces: (sum difference problem) the brother is (26+2)÷2= 14, and the brother is 26- 14= 12, and then restore:
(1) The elder brother gave back five pieces to the younger brother: 14-5=9 for the elder brother and12+5 =17 for the younger brother;
(2) The younger brother returns the half he took to his younger brother: if he takes half, the rest is the other half, so the elder brother should be 9+9= 18, and the younger brother is17-9 = 8;
(3) The elder brother returned half of the stolen money to the younger brother;
So the younger brother is 8+8= 16.
A: At first, my brother planned to choose 16.