What do you want to understand today?

PEAZIT Aha card

A triangle occupies half a parallelogram

Two identical triangles form a parallelogram. Divide base times perpendicular height by two.

A base of 8 cm and perpendicular height of 3 cm.

Relation	Meaning
S = a × h / 2	The height must correspond to the chosen base.
S = 8 × 3 / 2	Substitute lengths in the same units.
S = 12 cm²	Half of 24 cm² is 12 cm².

One worked example

S = a × h / 2The height must correspond to the chosen base.
S = 8 × 3 / 2Substitute lengths in the same units.
S = 12 cm²Half of 24 cm² is 12 cm².

Watch out: A sloping side is usually not the height. An obtuse triangle's height may meet an extended side.

Goal, prerequisites and card origin

What you will learn: Calculate area from a base and its corresponding height.

What you need first: Rectangle area and perpendicular lines.

An original PEAZIT working card. Independent expert review and effectiveness testing have not yet taken place. · v1

Show connections

Altitude and area of a triangle

Triangle — choose one side as the — Chosen base a

Chosen base a — has a perpendicular — Corresponding altitude h

Corresponding altitude h — makes with the base a — Right angle

Chosen base a — provides length a for calculating — Area A = a·h/2

Corresponding altitude h — provides perpendicular distance h — Area A = a·h/2

Two identical triangles form a parallelogram. Divide base times perpendicular height by two.

Without JavaScript, write your answer elsewhere before opening the solution.A triangle has a 6 cm base and corresponding height 5 cm. What is its area in cm²? Enter a number.

Solution — open after your own attempt

15 6 × 5 / 2 = 15 cm².

A question for your next return: The base is 7 cm and corresponding height 6 cm. What is the area in cm²? Enter a number.

Solution — open after your own attempt

21 7 × 6 / 2 = 21 cm².

Catalogue

Nothing here just yet.

Try a shorter search, another language or fewer filters.

Clear filters

Find your own way. Resources open directly on their authors’ websites. Order reflects search relevance, not a teaching-quality rating.

47,636 resources to explore

15 independent sources

3 resource languages

EXPLORE / EN

Where will curiosity take you?

Start with a subject. Then find your way.

All topics