Mr Jomo, I do want to learn why. I have never thought of that before.

The best 'because' that I can afford is because if all linear dimensions are doubled (width and length) then the result has to be doubled as well. Hence ft ^2.

What? So when you double 3 you get 3^2.

I take a long ruler and measure the height of my daughter and I find out that she is 21 inches tall.

My wife measure my daughter two weeks before me and marks her height on the wall. She was 19 inches tall then. Then she measure our daughter again right after I measured her (and found her to be 21 inches tall). She marks her new height on the wall and notices that the difference between the two marks is 2 inches. So she concludes that 19 in + 2 in = 21 in^2.

Do you see that the child can not be 21 inches tall and 21 square inches tall.

You will not understand this unless you know what square units are.

You need to start a new thread explaining via a drawing why 3 inches by 4 inches is 12 square inches and not 12 inches. Take me up on this if you really want to learn this.