A right triangle has an area of 13 m2. The dimensions of the triangle are increased by a scale factor of 3. What is the area of the new triangle?
39 m2
169 m2
117 m2
142 m2
I think it is A...?
nope. If each dimension is scaled by three, the area is scaled by 3^2, so (C).
recall that the area
a = 1/2 bh
If b and h are replaced by 3b and 3h, then
new area
A = 1/2 (3b)(3h) = 1/2 9bh = 1/2 bh * 9, or 9a