The height has been incorrectly determined. The correct height is 2 units. The area is 4 square units.
Practice makes perfect
We are asked to calculate the area of a triangle. We will then use the formula
A=1/2bh
where b is the triangle's base and h its height. Let's begin the solution by having a look at the triangle whose area we are going to calculate.
We are free to pick any of the three sides as our base. Let's pick BC. The height is always perpendicular to the base. Let's mark the height.
The triangle's base is parallel with the x-axis and therefore we can calculate its length using the Ruler Postulate.
We find that the base is 4 units which is the same as in the suggested solution. We now continue by determining the triangle's height. By counting grid lines we find
h= 2 units,
which differs from the value given in the suggested solution. The mistake they have made is that they instead of calculating the height have calculated the length of one of the sides. The correct area is therefore
A&=1/2bh
A&=1/2(4)(2)
A&= 4 square units.
