Area of Triangles worksheet for Grade 5 Maths, featuring six triangle problems with dimensions and a formula box.

Let’s solve each triangle one by one using the formula:

Area = ½ × base × height

We’ll pick the correct base and height for each triangle. Remember: the height must be perpendicular to the base (it forms a right angle with the base).

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Triangle b:

Looking at the diagram, it’s a right-angled triangle. The two sides forming the right angle are both 6 cm — so we can use either as base or height.

But wait — there’s also a dotted line labeled h = 8 cm, which is drawn from the top vertex down to the base of 6 cm. That means:

→ Base = 6 cm
→ Height = 8 cm

So,

Area = ½ × 6 × 8
= 3 × 8
= 24 sq cm

✔ Check: Even though it’s a right triangle with legs 6 and 6, that would give area 18 — but here the height given is 8 cm to the base of 6 cm, so we MUST use those values. The 10 cm side is the hypotenuse — not needed for area.

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Triangle c:

This triangle has sides 10 cm, 10 cm, and 8 cm. There’s a height labeled h = 9 cm drawn to the side of 8 cm.

So:

→ Base = 8 cm
→ Height = 9 cm

Area = ½ × 8 × 9
= 4 × 9
= 36 sq cm

✔ Check: The height is perpendicular to the 8 cm side — yes, shown by the dotted line meeting it at a right angle. So this is correct.

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Triangle d:

All three sides are 10 cm — it’s an equilateral triangle. But they’ve given us a height h = 6 cm drawn to one of the sides (which is 10 cm long).

So:

→ Base = 10 cm
→ Height = 6 cm

Area = ½ × 10 × 6
= 5 × 6
= 30 sq cm

✔ Check: Even though in reality the height of an equilateral triangle with side 10 is about 8.66 cm, here the problem gives h = 6 cm — so we use what’s given.

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Triangle e:

Base is labeled 6 cm at the bottom. Height is drawn as a dotted line inside the triangle, labeled h = 7 cm, going straight up to the top vertex.

So:

→ Base = 6 cm
→ Height = 7 cm

Area = ½ × 6 × 7
= 3 × 7
= 21 sq cm

✔ Check: The other sides (9 cm and 6 cm) are slanted — not needed. We only need base and its matching perpendicular height.

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Triangle f:

Base is 6 cm at the bottom. Height is drawn as a dotted line from the top vertex down to the base, labeled h = 6 cm.

So:

→ Base = 6 cm
→ Height = 6 cm

Area = ½ × 6 × 6
= 3 × 6
= 18 sq cm

✔ Check: The other sides (5 cm and 7 cm) are just extra info — ignore them. Use base and height given.

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Final Answer:

b. 24 sq cm
c. 36 sq cm
d. 30 sq cm
e. 21 sq cm
f. 18 sq cm