ok so area=162
since the triangles sides were cut out of a square, base=height
area=1/2bh=162
b=h
area=1/2b^2=162
times 2 both sides
b^2=324
sqrt both sides
b=18=h
the legnth of one side is 18cm
see diagram
another way, is total aera of square=areas of both triangles=162+162=324
remember area of square=side^2 so
324=side^2
sqrt both sides
18=side
answer is 18cm
