Maths Terms for 11-13 Yr Olds

A closed plane figure bounded by straight lines. The name derives from 'many angles'.

If all interior angles are less than 180 degrees the polygon is convex. If any interior angle is greater than 180 degrees, the polygon is concave.

If the sides are all of equal length and the angles are all of equal size, then the polygon is regular; otherwise it is irregular. Adjective: polygonal.

Symbol: lb. An imperial unit of mass. In the imperial system, 14 lb = 1 stone. 1 lb is approximately 455 grams. 1 kilogram is approximately 2.2 lb.

A 3D solid bounded by two congruent polygons that are parallel (the bases) and lateral faces formed by joining the corresponding vertices of the polygons. Prisms are named according to the base e.g. triangular prism, quadrangular prism, pentagonal prism etc. Example: If the lateral faces are rectangular and perpendicular to the bases, the prism is a right prism.

A mapping of points on a three dimensional geometric figure onto a plane according to a rule. Example: A map of the world is a projection of some type such as Mercator's projection. Plans and elevations are vertical and horizontal mappings.

A chain of reasoning that establishes the truth of a proposition.

1. A part to whole comparison. Example: Where £20 is shared between two people in the ratio 3:5, the first receives £7.50 which is 3/8 of the whole £20. This is his proportion of the whole.

2. If two variables x and y are related by an equation of the form y = kx, then y is directly proportional to x; it may also be said that y varies directly as x. When y is plotted against x this produces a straight line graph through the origin. If two variables x and y are related by an equation of the form y = then y is inversely proportional to x; it may be said that y varies inversely as x.

An instrument for measuring angles.

A solid with a polygon as the base and one other vertex, the apex, in another plane. Each vertex of the base is joined to the apex by an edge. Other faces are triangles that meet at the apex. Pyramids are named according to the base: a triangular pyramid (which is also called a tetrahedron, having four faces), a square pyramid, a pentagonal pyramid etc.

In a right-angled triangle, the square of the length of the hypotenuse is equal to the sum of the squares of the lengths of the other sides i.e. the sides that bound the right angle.

One of the four regions into which a plane is divided by the x and y axes in the Cartesian co-ordinate system.