Assume that the dimensions of the room in the plan are a (width ) by b (length),
such that a*b=30.
Since the scale is 1:100, a represents 100a, and b represents 100b.
So the actual dimensions are 100a by 100b.
The area is 100a*100b=a*b*10,000=30*10,000=300,000 (square units)
Answer: 300,000 (square units)