If a rectangle has length (x+3) and breadth (x+1), what is its total area according to the area model?

Correct answer: x²+4x+3

The correct answer is A: x²+4x+3. The area of a rectangle is length × breadth, so we calculate (x+3)(x+1). In the area model, split the length into x and 3 and the breadth into x and 1. The four smaller areas are x×x=x², x×1=x, 3×x=3x, and 3×1=3. Add them: x²+x+3x+3=x²+4x+3, because x and 3x are like terms. Option B leaves out the 3x contribution. Option C uses 2x even though the two cross-products are x and 3x, which total 4x. Option D has constant term 4, but the constant corner is 3×1=3, not 4. Thus A is the only complete expansion. Memory cue: for (x+p)(x+q), the middle coefficient comes from px+qx and the constant term is pq.