how do i solve?

Question

Find the area of the blue triangle if each square in the grid is 5 cm by 5 cm. Area =   square cm.

Answer 1

Hopefully you can see that you can make a rectangle by drawing a matching triangle on top of the blue triangle, just flipped around.

How would we find the area of the rectangle? It's 2 squares by 5 squares.

2(5) + 5(5) = 10 + 25 = 35

Buuuuut, the triangle is half of the rectangle.

35/2 = 17.5 cm²

Answer 2

The area of a triangle is:

Area - (1/2)base*height

The height is clearly 2 squares:

height = 10 cm.

The width is shifted left roughly 1/3 square, but it is 5 squares:

base = 25 cm

Area = (1/2)(25)(10) cm² = 125 cm²