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

0.1 cm (1 mm)

HintShare the gap equally between the divisions.

The whyThe 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

HintDivide the gap by the number of spaces.

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

175 ml

HintFind the value of one division first.

The whyEach division is 25 ml, so three of them are 75 ml, and 100 + 75 = 175 ml.

2.4 kg

HintEach mark is a tenth of a kilogram.

The whyFour marks are 400 g, which is 0.4 kg, so the reading is 2.4 kg.

17 °C

HintHalfway between two marks is the number midway between their values.

The whyWhen a reading falls between two marks, estimate its position. Halfway between 16 and 18 is 17.

A rhombus

HintIt looks like a square pushed sideways.

The whyIts opposite sides are parallel, its opposite angles are equal and its diagonals cross at right angles.

A trapezium

HintThink of the side view of a lampshade or a bucket.

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

6

HintCount the faces of a cereal box.

The whyA 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

HintTry wrapping the row round and then closing up both ends.

The whyFour 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

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

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