Activity: All in Your Head
Try working out the following problems in your head using the strategies from the previous activity.
Consider breaking down numbers to make easy addition problems.
For example,. Splitting the numbers up like this means that you can work in tens, which makes them much easier to add up in your head.
(a) Here are two different approaches you might try:
(c) Here, we could say that 29 is one less than 30, and 19 is one less than 20, so is two less than 30 + 20, or 50. So, the answer is 48.
Alternatively, you could write .
Here instead of spitting the numbers up to help us work in tens we have grouped them together to give us tens.
Want a little more practice with mental math? Check out this pencast on mental math (Click on “View document”).
You can practice these mental techniques in lots of different ways, but it is a good idea to start with easier problems and/or situations before you move forward. Get comfortable with the process and never be afraid to make mistakes. That’s how you learn! You might like to practice with your friends and family and see how you get on together.