3. From the 10 numbers , take out 3 numbers so that their sum is an even number not less than 10. The number of different ways to do this is .
Problem 690
Official solution
51
3. 【Analysis and Solution】The number of ways to choose 3 different kilometer numbers from these 10 numbers is ; the number of ways to choose 1 even number and 2 different odd numbers is .
The number of ways to choose 3 numbers from these 10 numbers such that their sum is less than 10 kilometers is as follows:
Therefore, the number of different ways that meet the requirements of the problem is