To solve the question we need to note that:
area scale factor=(linear scale factor)^2
linear scale factor=1:2:3
Area scale factor=1^2:2^2:3^2=1:4:9
Hence, given that the area of the smallest triangle is 72 sq. inches, the area of:
medium triangle will be:
4/1*72=288 sq. inches
largest triangle will be:
9/1*72=649 sq. inches