Area
The area is half of the base times height.
- "b" is the distance along the base
- "h" is the height (measured at right angles to the base)
Area = ½ × b × h
The formula works for all triangles.
Example: What is the area of this triangle?
(Note: 12 is the height, not the length of the left-hand side)
Height = h = 12
Base = b = 20
Area = ½ × b × h = ½ × 20 × 12 = 120
TRICK: WHEN YOU CALCULATE THE AREA OF TRIANGLE HALF BASE OR HEIGHT AND MULTIPLY . YOU CAN ORALLY CALCULATE THE AREA
EXAMPLE 2 
Now in this example half of 10 is 5 and 5 into 3 is 15
1. Height 18cm, base 9cm then Area ??
Half of 18 is 9 so 9×9= 18
Area= 18 cm2
2. Height 23cm, base 8cm then Area ??
Half of 8 is 4 so 23×4= 92
Area= 92cm2
3. Height 17cm, base 7cm then Area ??
Half of 7 is 3.5 so 17×3.5= 59.5
Area= 59.5 cm2
Practice
Find the area
1. H= 45, B = 8
2. H= 63, B = 6
3. H= 45, B = 18
4. H= 56, B = 9
1. H= 5, B = 11
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