Yes, an A3 paper is approximately equal to two A4 papers in size.
A3 paper has dimensions of 297 × 420 mm (11.7 × 16.5 inches), while two A4 papers placed side by side have dimensions of 2 × 210 × 297 mm (2 × 8.3 × 11.7 inches), which is roughly equivalent to the size of an A3 paper.