The topic Negative number addition and subtraction: word problems appears under the 7th grade (U.S.) Math Mission. This exercise does several types of word problems involving addition and subtraction with integers.
Types of Problems
There are three types of problems in this exercise:
- Determine if the net result is positive or negative: This problem provides a situation where a positive or negative amount is introduced or removed from an initial state. The user is asked to determine if the total will end up being positive, negative or neutral and select the correct option.
- Compare the two results: This problem provides counts on two different amounts which can be positive or negative. Users are asked to indicate which amount is larger and by how much it is larger.
- Describe how to cancel the number: This problem has a number and asks the user to select all ways to cancel that number. The possible answer choices are in a multiple select list.
Strategies
The number line model for negative can help on this problem, as can a set theoretic model. A working knowledge of addition and subtraction rules for integers is important.
- The Determine if the net result is positive or negative is often a problem about the charge of an atom.
- On the Compare the two results problem both values can both be below or above average (in which case the "difference" is the difference), or one can be above and one will be below (in which case the "difference" is the sum).
- The multiple select problem always has two answers, adding a number and subtracting it's opposite.
Real-life Applications
- Negative numbers are used to represent land below sea level.