to point out to the teacher that a square is a rectangle?

[GooseyLoosey]

Part of ds's homework was to draw on a grid 2 rectangles with a perimetre of 8cm. He drew a 3x1 oblong and a 2x2 square.

Aside from the fact these were the only possible shapes without using 1/2 squares, the teacher marked his homework as incorrect as a square was not a rectangle.

Ds (who is a perfectionist) read this and was not at all happy. He shouted "it is, I know it is, it is. Mummy, I'm right".

Would I be unreasonable to tell ds to ask the teacher why a square is not a rectangle? Or are we completely wrong and squares and rectangles are mutually exclusive?

(PS - I really don't expect teachers to always be right - God knows I am not but this teacher is the school's maths co-ordinator).

AFAIK, a square has 4 sides of equal length. A rectangle doesn't.

A square has 4 sides of equal length and 4 right angles. A rectangle has 2 sides of the same length and four right angles. They are not the same thing at all. The teacher is not wrong

A rectangle is any four-sided object with 4 right angles, so yes, this includes squares.

Hmm - I thought a square was a rectangle (as that's the generic term) but a rectangle wasn't usually a square...

But I failed my Maths 'o' level twice so what do I know?

Hurrah!!

Indeed - a rectangle has 4 right angles with 2 parallel sides of the same length. There is no requirement that the other sides have to be a different length so squares are a subset of rectangle (as far as I am aware).

personally I thought that the definition of a rectangle was 4 90 (degree) corners, and two pairs of parallel sides. That makes a square a subset of rectangles. I can see why you might want to not teach that, it's a bit confusing. However where you have a child bright enough to figure this out for himself then it needs to be dealt with.

I'm sure a primary teacher or mathematician will be along shortly though...

Should you wish to expand your mathematical knowledge, Euclidean geometry is always good fun.

A square must have four sides of equal length, whereas a rectangle has by definition different lengths, ie two sides longer than the remaining two sides. Therefore a shape of equal sides ie a square can't be a rectangle.

Agree with alpinepony, and i agree...teachers can be wrong, but a maths co-ordinator should not!!!

I agree with you and the semantics, but see this as a lesson about how people want the answers they have in their heads, rather than all the possible answers... and the teacher clearly can't think outside the box (pardon the pun : ) )

I think you'd be unreasonabe to say that, yes.

In asking for rectangles she clearly meant a rectangle, 2 longer, shorter sides.

You would be perfectly reasonable to point put that using her instructions i is not possible to draw 2 different rectangles. (although proably better if ds tells her, and asks for clarification)

Def of a rectangle is that it has four internal angles of 90 degrees each,its opposite sides are parallel and congruent, a square is a special type of rectangle in that it has four sides of equal length.

Well actually, you are right in that squares and rectangles are not mutually exclusive. All squares are rectangles (but not all rectangles are squares). Your son is correct.

www.mathwarehouse.com/geometry/quadrilaterals/parallelograms/is_square_rectangle.php

The teacher has chosen a stupid example actually, what else was he meant to do? An 8cm perimeter doesn't exactly give him loads of options - the only other one (working with "whole" numbers is to do a 1x3 oblong which is obviously the same shape. How old is your son?

Trying to see it from the teacher's point of view I guess she doesn't realise he understands the intricacies (not many children would I don't think), but is probably where she should have explained to him better - like I say though, she chose a daft example and is probably kicking herself!

When ds got the question he realised that it was impossible to complete the instructions unless a square was a rectangle so he looked it up. Having satisfied himself that it would be correct to draw a square, he drew one. Its hard for him to let it go.

I agree that a square is a rectangle.

It has 4 right angle corners, 2 sets of 2 parallel sides of equal length.

that's a rectangle

she should have specified she wanted non-square rectangles, or rectangles that fitted the rule that no more than 2 sides were the same length.

she shouldn't have marked him down, even if it's not hte type of rectangle she wanted. because he was not wrong.

(this is the problem you get when you try to simplify stuff)

I always thought that a square was a form of rectangle too. I checked on OED (which I know is a word dictionary, not a maths one) and it states: "1. A plane figure with four straight sides and four right angles, opposite sides being parallel and equal in length; esp. one in which adjacent sides are unequal, as contrasted with a square."

Does that make you both right?

My son is just about to turn 8 (he had already drawn a 1x3 oblong and was asked to do 2 shapes).

(I know I am being a bit picky really, but you had to witness his indignation at reading her response).

DH (former maths teacher) says that yes, a square is a rectangle.

x-posts with you Goosey - i suggest you get him to tell her that (or you could tell herthat)

A square is a special rectangle, a rectangle is a special parallelogram and your DS is especially clever.

A square is a rectangle

maybe she should have just said "oblong" and forgoed the mathematical names.

A square IS a rectangle but not all rectangles are squares

basic geometry

DS should ask the teacher why a square is not a rectangle in this case