Anyone have alesson for teaching this...Math 3rd grade

I dont knwo what you call this but for example... _ +2=10. How do you teach them( i mean I need a lesson step by step procedure to teach them) how to solve this?

Message edited 9/9/2011 9:20:41 PM.

Re: Anyone have alesson for teaching this...Math 3rd grade

I don't have a step by step lesson for you, but what about using manipulatives to help find the missing addend?

You could show the students that in order to find the missing addend it is necessary to balance what is found on both sides of the equal sign.

You could use 3 different colors. For example, using the problem you cited:
You could use 2 blue squares on one side... and show ten red squares on the other side. Students would then count out how many of a third color would need to be added in order to "balance" the equation.

From that point you could guide them to use subtraction, modeling with the manipulatives, in order to solve the problem.

Not sure if this was at all clear..lol...but I hope it helps. :)

Re: Anyone have alesson for teaching this...Math 3rd grade

We teach them to do the reverse operation on the other side vertically.

Re: Anyone have alesson for teaching this...Math 3rd grade

We teach fact families and triangles. The triangle has the sum at the top and the addends on the bottom corners. The family includes the 2 addition probs and 2 subtraction probs. So if they can figure out that one of the subtraction probs is 10-2 then they should be able to figure out the answer to your prob.

Re: Anyone have alesson for teaching this...Math 3rd grade

I teach it as a balance scale. Talk about what the equal sign means. What is on one side must be the same as what is on the other. Then use manipulatives to show how to balance the scale.
You can probably google missing addends for lessons.

Message edited 9/10/2011 2:21:02 PM.

Re: Anyone have alesson for teaching this...Math 3rd grade

It's basically algebra, except at that age they don't solve for 'x'. I would have them use manipulatives or draw a picture to show how many they need to add to 2 to get 10. I would also have them figure out 10 - 2 = ? to get the answer. I taught 3rd grade last year, and I remember my students having a tough time with this at first because it's pretty abstract for their age. But after some practice they got it and by the time of the state test it was easy for them. :)