Mental Math Addition and Subtraction

Mental Math 1

by Dr Tran

​The Basic Mental–Math Strategies

Mental computation may use one strategy or a combination of these three

strategies. For example, in making easy numbers, you may have to break up numbers. Or, to make easy numbers you may have to compensate.

Students should be aware of these strategies and be able to identify which

ones they’re using. There are three main strategies:

• ​MAKE EASY NUMBERS

• BREAK UP NUMBERS

• COMPENSATE​

​MAKE EASY NUMBERS

Easy numbers are numbers that are easy to compute without using a calculator or pencil and paper. Examples of easy numbers are numbers that end in 0, like 10, 20, 30, 40, 50. Here are some examples of numbers that are easy to add, subtract, multiply, and divide:

​BREAKING UP NUMBERS

Breaking up numbers means separating numbers to make them easier to compute. Here are some examples:

​BREAKING UP NUMBERS

Breaking up numbers means separating numbers to make them easier to compute. Here are some examples:

​COMPENSATION

​To compensate, you can do one of the following:

• Adjust one of the numbers and then adjust the answer.

• Adjust both numbers. Then it’s not necessary to adjust the answer.

Here are examples when one of the numbers and the answer are adjusted: