Predict the result
Chapter 2 connects the number line and midpoint.
How do you find the midpoint of three and eleven, negative four and ten,
and negative seven point five and negative two point three?
A midpoint is equally far from both endpoints.

Set up the model
Add the endpoints and divide by two.
Signed endpoints follow the same formula.

Work the example
Add three and eleven, then divide their sum by two to get seven.
Add negative four and ten, then divide their sum by two to get three.
For two negative endpoints, keep their signs when adding.
Negative seven point five plus negative two point three, divided by two, gives negative four point nine.
Its distance from each endpoint is two point six.

Check the result
Now find the midpoints of the three check pairs.
Take eight seconds to think before the answer appears.
[Eight-second silent pause to work; the answer remains hidden.]
Their midpoints are nine, one, and negative one point nine.
Each result is halfway between the original endpoints.

Interpret the result
A midpoint is an average, while distance measures separation.
Use the original task and check that your result fits its meaning.