A rectangular cardboard is 47 mm by 9 mm. A square of side 5 mm is cut from it. What area remains?
Note
First find the rectangle area: 47 × 9 = 423. The cut-out square area is 5 × 5 = 25. Remaining area = 423 − 25 = 398 square mm. For composite figures, split the shape into simple parts or subtract the removed part. Here the square is cut out, so its area must be subtracted from the rectangle area, not added. So the correct choice is 398 mm².