 
       
      
    7. The length x of a rectangle is decreasing at the rate of 5 cm/minute and the width y is increasing at the rate of 4 cm/minute. When x = 8cm and y = 6cm, find the rates of change of (b) the area of the rectangle.
 
                
                  Given same as previous question
Solution:-
Area of rectangle = xy
      
Hence, the rate of change of area is   
 
                 
                