Question

from a rectangular metal sheet of size 20cm by 30cm, a circular sheet as big as possible is cut.find the area of the remaining sheet.

Answer 1

diameter of largest circle = length of the smallest side of rectangle 
try to visualize otherwise the circle wont fit in the rectangle. 
initial area = l*b=30 *40=1200 
final area =initial - area of circle=1200-3.14*15*15=493.5 
Hope it helps you