area=1/2 times base times height
remember that 45-45-90 triangle has sides of x,x and x√2
(legs are measure x and hypotonuse=x√2)
the legs are equal and are also the base and height
find the legs (x=leg)
hypotonuse=24
24=x√2
divide both sides by √2
24/(√2)=leg=base=height
volume=1/2 times base times heigth
V=1/2 times (24/√2) times (24/√2)
V=1/2 times (576/2)
V=576/4
V=144 units^2
answer is A