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6.01 Area of triangles

Worksheet
Area of triangles
1

Consider the rectangle shown:

a

Find the area of the entire rectangle.

b

Find the area of the triangle.

c

What do you notice about the two areas?

2

For each of the following figures:

i

Find the area of the entire rectangle.

ii

Find the area of the shaded triangle.

a
b
c
d
e
f
3

Consider the following triangle:

Which dimension of the rectangle forms the height of the shaded triangle?

4

Find the area of the following triangles:

a
b
c
d
e
f
g
h
5

Find the area of a triangle which has the following dimensions:

a
Height =8\text{ in} and base =9\text{ in}.
b
Height =4\text{ yd} and base =6\text{ yd}.
c
Height =7\text{ mm} and base =8\text{ mm}.
d
Height =3\text{ cm} and base =9\text{ cm}.
Dimensions from area
6

For each of the following triangles, find the value of b or h given the area:

a

Area =20\text{ mm}^2

b

Area = 120 \text{ mm}^2

c

Area = 12 \text{ mm}^2

d

Area =48\text{ m}^2

e

Area = 54 \text{ cm}^2

f

Area = 120 \text{ cm}^2

7

Determine whether the following could be the dimensions of a triangle with an area of 20\text{ in}^2:

a

Base =8\text{ in}, height =5\text{ in}.

b

Base =1\text{ in}, height =20\text{ in}.

c

Base =5\text{ in}, height =8\text{ in}.

d

Base =2\text{ in}, height =20\text{ in}.

8

Complete the following table of base and height measurements for different triangles, which all have an area of 30\text{ m}^2:

\text{Base (m)}1015
\text{Height (m)}12
\text{Area (m}^2)303030
Applications
9

The faces on a 4-sided die are all triangular. Each face has a base length of 19\text{ mm} and a perpendicular height of 12\text{ mm}. Find the area of one face of the die.

10

Lisa has purchased a rectangular piece of fabric measuring 6\text{ yd} in length and 9\text{ yd} in width. Find the area of the largest triangular piece she can cut out from it.

11

A gutter running along the roof of a house has a cross section in the shape of a triangle as shown:

If the area of the cross section is 40\text{ cm}^2, and the length of the base of the gutter is 10\text{ cm}, find the perpendicular height h of the gutter.

12

Deep sea divers are scanning an area of the sea bed where a boat capsized. They want to get to point P, which is h meters above the sea bed.

At this point, they can cast a light out to view 9 meters across the sea bed and a cross sectional area of 45 \text{ m}^2 of water. From side-on, the light casts a shape that looks like the diagram below. The divers descend at a rate of 1.2 meters per second.

a

Find h, the distance of the divers from the sea bed at point P.

b

If the divers were descending directly downwards, how high above the sea bed were they 6 seconds before they reached point P?

13

At the entrance of the Louvre museum is a glass structure in the shape of a square base pyramid.

A replica of this pyramid is to be built such that each triangular face of the pyramid measures 7.5 meters at the base, and has a perpendicular height of 10 meters.

The faces will be made up of identical triangular glass tiles tessellated to fit exactly on each face.

a

Find the total area that needs to be covered with the triangular glass tiles.

b

How many glass tiles will be needed in total if each triangular tile measures 15 \text{ cm} across the base and has a perpendicular height of 20 \text{ cm}?

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Outcomes

MA.6.GR.2.1

Derive a formula for the area of a right triangle using a rectangle. Apply a formula to find the area of a triangle.

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