How To Always Know If Your Answer Is Right

You look at the answers, right? WRONG. What if it is a test? Do you just assume your answer is correct or is there a better way to do it? Students usually finish a question and then come to me to find out if they got the answer correct (If there is no mark scheme). They often get numbers they are not sure about or ones they did not expect. So they find me and find out if they did it right or not.

My reply.

`Is it realistic?`

`Does that answer make sense for that question?`

PART 1-Does my answer make sense in real life

You see I generally always know if you have the right answer or not just by looking at it. This makes me sound like a genius (Sadly Not). But there is actually a little trick that makes it easy and you learnt it YEARS ago. It`s called estimation. Say you have done a question about finding the mass of a truck. You get the answer 10kg. Now hopefully most of you should be able to realise that is far too small. A truck will have a mass much bigger than that. Good, most of you have the right idea. What we have just done is proven using common sense that the answer we have got is wrong. So we do the question again and we get 1000Kg. What do we do now?

This is where having a bit of life experience and knowledge about things outside of school comes in. I know that 1000kg is the same as a ton. I have heard that lorry`s usually have a mass of several tonnes. Therefore I can figure that my answer is still probably wrong.

Of course, there is a limit to this technique. You need to have some background knowledge. You will also never know if the answer is 5000Kg or 4000Kg. But there is another way to figure it out.

Part 2-Use mental maths to estimate the answer

Imagine if the question said that the lorry`s weight was 47075N. You know that to calculate the mass you just divide the weight by the strength of gravity. 9.81. A reasonably easy question. So you do it and you get an answer of 4000Kg. You need to check if it`s right. The basic way of checking is to round both of those numbers before you divide them. So instead of 47075N, we will have 48000N (Rounded it to the nearest thousand) and instead of 9.81 we have 10.

We quickly divide 48000 by 10 in our head (Just knock a zero off the end) and we get 4800Kg. Clearly our original answer must be wrong. When we do the proper calculation again, we get 4799Kg. This is how you can check to see if you are right.

You should always know roughly what the answer will be to a question before you answer it. That way you always know if you are right or wrong.

If you have any questions about using this technique, please message me.