Question

If the height of a trisngle is decrased by 40% and its base is increased by 40%, what will be the percentage change in its area?

Answer 1

Let initial base=b,
            height=h
area, A₁ = 0.5 bh

after height is decreased by 40% and base is increased by 40%,
base = 1.4b
height = 0.6h
Area, A₂ = 0.5×1.4b×0.6h = 0.42 bh

A₂ - A₁ = 0.42 bh - 0.5 bh = -0.08 bh
-ve sign indicates that area decreased.

% decrease = (0.08bh/0.5bh)×100 = 16%