I took the class on mathematical tasks and learned a few more things. In addition to ones like you have dogs and chickens. There is a total of 40 heads and 96 feet. How many dogs are there? This one is actually on the internet. I know because the reading teacher who helps out wanted to try it and found it on the internet. I am glad to know this because one of my students found it on the internet and copied everything down word for word. I would have known by the language in the explanation, even if I had not known it was on the internet. I think if I use this again, I will change the animals so they won't find it on the internet.
The presenter also offered some short tasks that can be given during class and shouldn't take more than 5 mins. You have a 3 x 5 card and three dice. You fold the 3 by 5 card in half like a hamburger bun. You line the three dice up so that all the 7 exposed surfaces add up to 23. This can take some time and it helps develop both problem solving skills and mathematical vocabulary when you write up how you came up with the answer.
Some of the places recommended for having good tasks like these include:
School improvement network
I plan to check each of these sites out for tasks.