Why is area called this ?

Question

to find the area of a rectangle,you multiply the lenth by the width. Why is area called a derived quantity?

Answer 1

because it is found by multiplying length by width. and it is a number.

derived just means found by means of something else.  in this case multiplication.

Answer 2

3. to reach or obtain by reasoning; deduce; infer.  

Quantity= unit of measurement.

L= 2 ft

W= 2 ft

Area= 4 ft ^2