LLL - Measurement
Circle Area and Prism Volume
Find the radius before using circle area, then find the depth before calculating prism volume.
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Point it out, then calculate.
Circle area starts with radius. Prism volume starts with the cross-section area and the depth through the prism.
40circle radius and area questions
10depth identification questions
30rectangular and hexagonal prism questions
Area of a circle
A = 3.14 x r x r
If the diameter is given, halve it first to get the radius.
Volume of a prism
V = cross-section area x depth
For a hexagonal prism in this lesson, the hexagon area is already given.
Circle rule
Area of a circle starts with radius
Use pi as 3.14 in this lesson. Radius is from the centre to the outside edge; diameter goes all the way across.
Radius given
If r = 5 cm, then A = 3.14 x 5 x 5 = 78.5 cm^2.
Diameter given
If d = 12 cm, then r = 6 cm before using A = 3.14 x r x r.
1click the radius
2find the radius value
3write 3.14 x r x r
4use square units
Prism rule
Volume is cross-section area times depth
A prism has the same cross-section all the way through. The depth is the distance the shape travels through space.
Step 1: end face
For rectangles, calculate the front area. For hexagons, the area will be given.
Step 2: depth
Volume = cross-section area x depth.
1identify the end face
2click the depth
3multiply by depth
4use cubic units
Section
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Question 1 of 80
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Complete
Measurement summary
The two big rules are A = 3.14 x r x r and V = cross-section area x depth.
0 / 10radius clicks
0 / 10radius values
0 / 20circle area
0 / 10depth clicks
0 / 30prism volume