Taking Imperial measures


I am one of the Imperial people! I was brought up on feet and inches and have no real feel for the new measures. When someone mentions a length in centimetres I find it difficult to imagine. I know there are 2.5cm for each inch. Can you make any suggestions that might help me?


The day I received your letter I had just been running a Mathagony Aunt Clinic at Coombe Dean Comprehensive in Plymouth for "maths-afraid" parents and their children. Having been asked by parents on previous courses to help them with metric measures I included this in the session. I got them to estimate the lengths of different pieces of string in both inches and centimetres. Each person had an envelope with three pieces of pre-measured string, labelled A, B and C. Not surprisingly the adults were more accurate with the inch estimations and the children the centimetres.

To provide yourself with a good "crib" ruler, first measure your body. Find a 1cm part, a fingernail perhaps, a 10cm part, your hand maybe and so on. A good metre (100cm) measure is probably from your fist with your arm outstretched to the centre of your chest.

But remember that we are all different shapes and sizes, so you must actually measure yourself. This is quite a good guide when your are out shopping for furnishings or the garden.

A woman at the session explained that she does a lot of needlework and that she had to do a lot of converting from centimetres to inches and vice versa. This is how she explained her method:

"There are 2.5 centimetres to 1 inch. There are more centimetres than inches so you multiply by the big number. So, for changing inches to centimetres, multiply by 5 and divide by 2 (the order doesn't matter) (x 5 then V 2). This is the same as multiplying by 2.5." For example 7 inches would be 17.5cm: 7 x 5 = 35. 35 V 2 = 17.5.

A teacher in the group pointed out that it might be easier to multiply by 10 and divide by 2 and divide again by 2 (x 10 then V 2 and V 2). Halving and halving again makes it easier to do in your head.

For changing from centimetres to inches there are fewer inches so you divide by the big number: divide by 5 and multiply by 2 (V 5 then x 2) or (V 10 then x 2 and x 2).

Have a go! With practice you will find that you become quite quick.


I teach maths in a comprehensive school. I don't have a degree in maths as I did a BEd with maths as my main subject. Obviously I did A-level maths, but the reason I am writing is I am feeling that my pupils don't rate my ability. This has been a feeling that has become more obvious over the past month or so. The mother of one of the pupils in my Year 8 class is a maths teacher. She sent her daughter to school with a problem that she had done with her pupils and told her daughter to ask me to solve it.

I have been busy running after-school workshops for SATs and support groups for GCSE pupils and haven't had time to give it proper attention. The pupil has told her friends that her mum solved the problem in about two hours. Each lesson she asks me if I have solved it yet and I have to say no. It isn't what she says, it is the way that she looks and her friends look. I am feeling really stressed about it. I am sure I am being judged.


I sympathise wholeheartedly. You don't mention in your letter if you actually enjoy solving problems and you didn't send me the problem. There are so many constraints on our time and your priority was your SATs and GCSE pupils: this needs to be made clear to the Year 8s. Tell them that next year it will be their turn for that kind of support.

So what might I have done to avert the problem occurring?

* Pinned it up on the staff noticeboard with the offer of a mini-prize for first correct solution to my pigeon hole.

zTaken it to the maths department meeting and told them the story and suggested they might like to have a go (assuming that they are not all flat-out busy too).

* Given the problem to my other classes (there is always a smart cookie who will really enjoy the challenge).

To raise your profile a bit with this group find a similar problem that will be a challenge and set it for them - and pass a copy along to the girl's mother. If you can't think of a suitable one, enrol the help of the rest of the maths team. Good luck!

More on mass and weight

I read your column on mass and weight (TES Teacher, May 3) with interest. Another approach might be to point the French teacher's pupil at H G Wells's short story "The Truth about Pycraft", in which the obese Pycraft successfully consumes a magic potion to reduce his weight, only to discover that his mass has not changed. A weightless barrage balloon, he is forced to wear lead underpants to keep his feet on terra firma.

Mike Trolan, Northumberland

Wendy Fortescue-Hubbard is a teacher and game inventor. She has been awarded a three-year fellowship by the National Endowment for Science, Technology and the Arts (NESTA) to spread maths to the masses.Email your questions to Mathagony Aunt at teacher@tes.co.ukOr write to TES Teacher, Admiral House, 66-68 East Smithfield, London E1W 1BX

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