2.OA.C.3
Determine whether a group of objects (up to 20) has an odd or even number of members, e.g., by pairing objects or counting them by 2s; write an equation to express an even number as a sum of two equal addends.
Students will learn how to determine whether a group has an even or odd number of items. They will also practice division by two using manipulatives and visual models. Use ten frames and the idea of sharing a number of objects between two people, to explain even and odd. If both people receive the same amount, then the number of objects was even. Otherwise it was odd. Here's a demonstration. Have kids practice identifying even and odd numbers. Start by giving them pictures of ten frames and asking whether the number is even or odd. Then give them numbers and let them construct the ten frame to determine the number's parity. Then teach them how to divide even numbers by 2 by reading the number of columns in a ten frame.
Next, give your students this challenge.
After that, have students play this Nim-like game.
Once they've found the optimal strategy to that game, have them explore the vanilla version of this game, which is also Nim-like. Start by playing the game with 6 nuts and 6 raisins and attempt to find the optimal strategy. If your students are struggling, have them figure out who must win if there is 1 nut and 1 raisin, 2 nuts and 2 raisins, etc. What's the pattern?