Geometry and measures, Year 7: reading scales and naming shapes

0.1 cm (1 mm)

提示Share the gap equally between the divisions.

为什么The gap is 1 cm and it is split into 10 equal parts, so each part is 1 ÷ 10 = 0.1 cm, which is one millimetre.

25 ml

提示Divide the gap by the number of spaces.

为什么The gap is 100 ml and there are 4 spaces, so each is worth 100 ÷ 4 = 25 ml.

175 ml

提示Find the value of one division first.

为什么Each division is 25 ml, so three of them are 75 ml, and 100 + 75 = 175 ml.

2.4 kg

提示Each mark is a tenth of a kilogram.

为什么Four marks are 400 g, which is 0.4 kg, so the reading is 2.4 kg.

17 °C

提示Halfway between two marks is the number midway between their values.

为什么When a reading falls between two marks, estimate its position. Halfway between 16 and 18 is 17.

A rhombus

提示It looks like a square pushed sideways.

为什么Its opposite sides are parallel, its opposite angles are equal and its diagonals cross at right angles.

A trapezium

提示Think of the side view of a lampshade or a bucket.

为什么The two parallel sides are usually different lengths. The other two sides are not parallel, so they would meet if extended.

6

提示Count the faces of a cereal box.

为什么A cuboid has a top and a bottom, a front and a back, and two sides. Its net shows all six rectangles laid flat.

No — faces would overlap and two sides stay open

提示Try wrapping the row round and then closing up both ends.

为什么Four squares in a row wrap round to make a tube. The fifth and sixth then land on top of squares already used, and nothing is left for the two ends.

4

提示Count how many times it fits its own outline in one full turn.

为什么A square looks identical after each quarter turn: at 90°, 180°, 270° and 360°. That is four positions in a full turn.