Open Middle®
Directions: Using the digits 1 to 5, at most one time each, fill in the boxes to create a true number sentences with the greatest possible sum.
Hint
What is the largest sum you could have?
What are the largest addends you could use?
What’s an example of addends you couldn’t use? Why not?
What are the largest addends you could use?
What’s an example of addends you couldn’t use? Why not?
Answer
Because the digits are limited to 1 to 5, the largest sum you could make is 5. That results in:
1 + 4 = 5
4 + 1 = 5
3 + 2 = 5
2 + 3 = 5
This gives you an opportunity to talk about the commutative property of addition (for example: 1 + 4 = 4 + 1) and how there are bigger sums if you use digits beyond 1 to 5.
Source: Robert Kaplinsky
I’m excited to give these to my daughter tomorrow. She’s in kindergarten and very bored with the “one more, one less” worksheets that get sent home. I printed off some of the addition and subtraction timed tests (that I don’t think anyone should ever give in an actual timed setting, but they’re still out there for kids who are hungry for any kind of math), but she got bored with those too.
I’m hoping the extra thinking involved in Open Middle problems will keep her entertained and loving math!
Hope I haven’t missed something here, but couldn’t you use 4 and 3 to make a sum of 7?
Thank you for asking that question Amber. I was thinking the same thing. Are we reading the question wrong? 🙂
Yes, I think you could use 4, 3 and 7, but the directions specify numbers less than 5 . wondering if it should be less than or equal to 5?
You can’t use 3 and 4 because you don’t have a 7 to put in the sum box. You only can use the digits 1 through 5
I would love to use this for a morning question. On the board as families come in to school one of the next few mornings]