Shape Flashcards
Perimeter = ?
Total length around the outside of a shape
Area = ?
The total space inside the shape
What is area measured in?
Cm^2
How do you work out area of a rectangle?
Base x height
How do you work out area of a triangle?
(Base x perpendicular height) /2
How do you work out area of a parallelogram?
Base x perpendicular height
In a circle, what is origin?
Centre of circle
In a circle, what is arc?
A part of the circumference
In a circle, what is tangent?
Touches circumference at one point
In a circle, what is chord?
Line that goes across, but not through the middle of circle
In a circle, what is sector?
Has to go from the centre
In a circle, what is circumference?
The distance around the edge of a circle
In a circle, what is diameter?
The distance from one edge of the circle to the other, passing through the centre
In a circle, what is radius?
The distance from the centre of the circle to the edge
What is the equation for circumference?
2x(Pi)xradius
Circle has a radius of 2.1m. What’s the circumference?
R =2.1m C = 2pir C =2 x pi x 2.1 /calculator C = 13.2m
A circle has a diameter of 6mm. What is the circumference? Leave your answers in terms of pi.
Diameter = 6mm radius = 3mm
C =2pir
C = 2x pi x 3
C= 6 pi mm
When should we leave our answer in terms of pi? Why?
During a multi step question, to avoid rounding errors
A circle has a circumference of 14m. What is the diameter?
C = 2 pi r 14 = 2 pi r / divide by 2 pi 14/2 pi = r 2.23m = r
A bicycle wheel has a diameter of 80cm. How many revolutions does the wheel do around a 400m track?
Revolution = 1 circle of the wheel 1 revolution = circumference C = 2 pi r C =2 x pi x 40 C = 80 pi cm R = 80 / 2 = 40cm
Track = 400m x 100 = 40, 000 cm Revolutions = 40000 / 80pi = 159.2 revolutions
How do you work out the area of a circle?
Area = r^2 x pi
Work out the area of a circle with a diameter of 20cm
R = 20/2 = 10
A= 10^2 x pi
=314.2cm^2
Your shape is a rectangle with a semi circle at one end. Work out the perimeter and area of the shape, when the base is 40cm and the height of the rectangle is 80cm
Perimeter
Semicircle = (2xpixr)/2 = (2xpix20)/2 = 20pi
Leave in terms of pi to avoid a rounding error
P=80+80+40+20pi
=200+20pi
=262.8cm
Area Rectangle: 80x40=3200cm^2 Semicircle: (pixr^2)/2 = (pix20^2)/2 = 200pi cm^2 A= 3200+200pi =3828.3cm^2
What is a trapezium?
A 4 sided shape with 1 pair of parallel lines
How do you work out the area of a trapezium?
(a+b)/2xh
(Parallel side + parallel side)/2 x perpendicular height
Find the area of a trapezium. Parallel sides: 5cm and 6cm. Perpendicular height:3cm.
Area = (5+6)/2 x3
=16.5cm^2
Calculate one length of a square of an area 196cm^2
X^2 = 196cm
Square root of 196 = x
X=14cm
What is a sector?
A section of a circle, starting from ten centre.
Find the area of a sector of a circle, where the bottom length is 10cm and the angle next to the centre is 70*
You have 70/360 of a circle Area = pi x r^2 =70/360 x pi x 10^2 = 61.0865... =61.1cm^2
Find the perimeter of a sector where the base length is 10cm, and the angle next to the centre is 70*
Circumference = 2 x pi x r
70/360 x 2 x pi x 10
= 12.2173…
Perimeter = 12.2173… + 10 + 10
= 32.2173…
