SME
Grade 6 Math · Problem type
Area of triangles
Use this for “A triangle has base 3 and height 7. What is its area?”
Diagram
Area: 30 cm².
Two copies make a parallelogram 10 by 6: the triangle is half.
Leaning the shape keeps the base, the height and the area.
This is an example. Type your own values to start a new problem.
A (cm²)
=
½
×
b
×
h
Formulas
A
=
1
2
×
b
×
h
(area
=
half
of
base
×
height)
30
=
1
2
×
10
×
6
Assumptions
•
Two copies of a triangle make a parallelogram, so a triangle is half of base × height.
•
In an obtuse triangle the height can fall outside the triangle.
•
The height meets the base (or its line) at a square corner.
Step-by-step
WE KNOW
b = 10 cm (base), h = 6 cm (height)
FIND
area (A)
Step 1 · Find area (A)
Use A = ½ × b × h (area = half of base × height)
Half of the parallelogram two copies would make.
A
=
1
2
×
10
×
6
A
=
5
×
6
A
=
30
cm²
Check
Put the numbers back in. Both sides should match.
30
=
1
2
×
10
×
6
✓
Topic check
See what you know: 5 questions on this topic
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Related lessons
Area of triangles, parallelograms and trapezoids
Main lesson
Area of trapezoids
Use this for “The bases are 9 and 15, the height 8. Find the area.”
Area of composite figures
Use this for the area of a house shape: a rectangle with a triangle on top.
Which segment is a height?
Use this for “Which segment is a height for this base?”