421 ÷ 35 × 299.97 ÷ 25.05 = ?2

Answer: Option D

$$\begin{array}{rl}& \text{Let the number be }x\\ & \text{Given }\\ & 421÷35\times 299.97÷25.05=x^2\\ & \approx {\left(x\right)}^2=420÷35\times 300÷25\\ & \approx 12\times 300÷25=12\times 12\\ & \approx x^2=12\times 12\\ & \therefore x=\sqrt{12\times 12}=12\\ & \text{Hence the number is 12}\end{array}$$