John can finish a certain job in three hours and chris can finish it in two hours how many hours will it take them to finish the job if they work together

I think its 2 and a half hours. Because found their average/mean. I did this by adding both their hours together 3+2=5 and then divided 5 by 2 which equals 2.5. Thats how you find the mean /average. You just add up all the numbers and then divide it by how many numbers there were. In other words its the sum divided by the count. Hope that helped :)