If the length of a rectangle is increased by 10 and the breadth decreased by 5 the area is unchanged If the length is decreased by 5 and the breadth increased by 4 even then the area is unchanged?

Suppose the dimwnsions of the rectangle are L and B

Then area = LB.

Now (L+10)*(B-5) = LB so that 10B-5L = 50

and (L-5)*(B+4) = LB so that -5B+4L = 20

Solving these two equations simultaneously, gives L= 30,B = 20