Discover Mathematics P4: Term 2, Units 9–13, Review
GoalReview bar graphs, line plots, lines, symmetry, triangles and quadrilaterals with new problems.
New words
line plot · a number line with a dot for each measurement; fractions can mark the stepsline of symmetry · a fold line that makes two halves that match exactlyperpendicular · making a right angle, a square corner
Explanation
Data: a bar graph shows how many in each category; a double bar graph compares two groups; read the title, key and scale first. A line plot with fractional steps shows measurements on a number line, one dot for each; to find a total, multiply each measurement by its number of dots and add. Shapes: a polygon is closed with straight sides, and its perimeter is the sum of its sides. A line goes on both ways, a ray starts at an endpoint, and a segment has two endpoints. Parallel lines never meet; perpendicular lines make a right angle. A line of symmetry folds a shape into two matching halves. Triangles are named by sides (equilateral, isosceles, scalene) and by angles (acute, right, obtuse). Quadrilaterals are named by parallel sides, equal sides and right angles: square, rectangle, rhombus, parallelogram, trapezoid.
Word
Remember
parallel
never meet, same distance apart
perpendicular
cross at a right angle
isosceles
at least 2 equal sides
trapezoid
exactly 1 pair of parallel sides
perimeter
sum of all the sides
Worked examples
The reading corner counts books borrowed by two classes. Sunday: 4A 12, 4B 9. Monday: 4A 7, 4B 11. Tuesday: 4A 10, 4B 10. On Monday, 4B borrowed 11 − 7 = 4 more books than 4A. In all, 12 + 9 + 7 + 11 + 10 + 10 = 59 books were borrowed.
Nine recipes use rice: 4 recipes use 1/2 cup, 3 recipes use 1 cup and 2 recipes use 1 1/2 cups. Total rice = 4 × 1/2 + 3 × 1 + 2 × 1 1/2 = 2 + 3 + 3 = 8 cups.
A rectangular yard is 8 m long and 5 m wide. Perimeter = 2 × (8 + 5) = 26 m. Area = 8 × 5 = 40 square metres. Opposite sides are parallel, neighbouring sides are perpendicular, and the dashed lines are its 2 lines of symmetry.
Class activity
Build a shapes poster. On one page draw a rectangle, a rhombus, a parallelogram, a trapezoid and three triangles (equilateral, isosceles, scalene). Under each write its name and its clues. Draw its lines of symmetry with dashed lines. Count them and write the number. Which shapes have no line of symmetry?
Practice
1
Name a triangle with sides 6 cm, 6 cm and 6 cm and a triangle with sides 3 cm, 4 cm and 5 cm.
The first is equilateral. The second is scalene (all sides different).
2
How many lines of symmetry does a square have?
4.
3
A quadrilateral has sides 7 cm, 5 cm, 7 cm and 5 cm. Find its perimeter.
7 + 5 + 7 + 5 = 24 cm.
4
Two lines cross and make a square corner. What are the lines called?
Perpendicular lines.
5
In a bar graph each block stands for 5 pupils. A bar is 7 blocks long. How many pupils is that?
