Adding and subtracting: Video playlist

You can’t always use a calculator or a pen and paper to work out a sum.

Sometimes you have to work it out in your head.

Sometimes it’s even faster.

There is only one rule when it comes to mental maths, if it works for you, then do it.

But here are some suggestions to get you going.

It’s easier to add together whole groups of ten, so we can put this six to one side, and that gives us 50.

Don’t throw that six away though, we are going to need it later.

Now we are left with 20 plus 50 which gives us 70. Now let’s bring that six back and we have our total.

You can use whole groups of ten to make subtraction simpler as well.

If we change this eight to a ten by counting on two, we make it easier to subtract.

Just remember to hold on to that two. So 46 take away ten equals 36. Now add on our final two to give us our answer of 38.

Also with subtraction you can count on from the lowest number to the highest to find your answer.

So with 30 minus 27 you can count on from 27 to 30 to give you the answer of three.

Very impressive, Albert.