Mathematical Olympiad in grade six of primary school 1. In the first 50 natural numbers, arbitrarily take two different numbers and add them together. How many different ways are there when the sum is even? 2. Only brackets, addition, subtraction, multiplication and division can be added. Write a formula with the number of 3, 3, 8 and 8 and the result is 24 Thank you for your answer. Could you be more specific in the first question?

Mathematical Olympiad in grade six of primary school 1. In the first 50 natural numbers, arbitrarily take two different numbers and add them together. How many different ways are there when the sum is even? 2. Only brackets, addition, subtraction, multiplication and division can be added. Write a formula with the number of 3, 3, 8 and 8 and the result is 24 Thank you for your answer. Could you be more specific in the first question?

There are 25 even odd numbers in the first 50 natural numbers. The sum of any two even numbers and any two odd numbers is even. The first even number can be added to the following 24 even numbers, and the second even number can be added to the following 23 even numbers. There are 1 + 2 + 3 + 4 +... + 22 + 23 + 24 methods, There are also 1 + 2 + 3 + 4 +... + 22 + 23 + 24 methods for odd numbers. There are 600 methods for odd numbers
2 、 8 ÷ (3 - 8 ÷ 3)=24
Who talks about permutation and combination in primary school? That's high school knowledge. I'm a math teacher in primary school, just like I do