Anil bought 6 exercise books at Rs 40 each and an eraser for Rs 10, He gave a Rs 500 note to the shopkeeper for the payment. How much change did the shopkeeper return him?

The area of a rectangle is 10 cm^2. one side of the rectangle is x cm. express the perimeter of the rectangle in terms of x and show that this rectangle cannot have a perimeter of 12 cm. the perimeter of the rectangle in terms of x is __ cm