Mindfucking triangle

What is the area of the big triangle below?

Some people will go cheyyyyyy... so easy... primary 3 kid also can solve this problem... Okok.. good good... let's try to work this out...

We learned in primary/secondary schools that...

Area of big triangle = Red area + blue area + green area + yellow area..

Bingo!!

So far so good..

Now.. let's try to rearrange the colored blocks like this...

OMG!!... for the same big triangle... the area is now...

Red area + blue area + green area + yellow area + white grid ???

Huh??? So do i add the white grid or not???

Ok... this is really mindfucking.. and till now i haven figured it out... haha.. =( =X

PS: All these mindfucking thingys are making me feel dam STUPID.. Seriously!