Directions: Fill in the blank with a number that makes the equation true.

4 + 5 = ___ – ____

### Hint

### Hint

If I cover the right side of the equation, what is 4 + 5 the same as? So, how much more do we need on the right side to make it the same as 4 + 5?

### Answer

### Answer

Many possibilities. As long as the difference is 9.

Some of the solutions are:

10-1,

Some of the solutions are:

10-1,

9-0,

12-3,

20-11

and so on…

### Extension

### Extension

How many different sets of numbers can go in there?

Source: Nanette Johnson

I don’t see how this is an “open middle” question. Wouldn’t it be more interesting to ask the child how many ways can we make this equation true (4+5= _ + _ )? What if we changed the “+” on the right to a “-” ? Then how many answers could we get? These questions could really get kids thinking.

Great suggestion. I made the change. Thank you for making the problem better.

I really liked the problem as it was for my 1st grade daughter- it let her develop a different understanding of the equal sign, and with a variety of examples tried she demonstrated her thinking in different ways which grew in sophistication.