If $(1+2x+3x^2)^{10} = a_0+a_1x+a_2x^2+\ldots+a_{20}x^{20}$,then $\frac{a_2}{a_1}$ is equal to

$A$ metal is burnt in air and the ash on moistening smells of $NH_3$. The metal is

Which logic gate is represented by the following combination of logic gates?

An earthquake generates both transverse $(S)$ and longitudinal $(P)$ waves in the earth. The speed of $S$ waves is about $4.5 \, km/s$ and that of $P$ waves is about $8.0 \, km/s$. $A$ seismograph records $P$ and $S$ waves from an earthquake. The first $P$ wave arrives $4.0 \, min$ before the first $S$ wave. The epicenter of the earthquake is located at a distance of about ..... $km$.

Which of the following is a bactericidal antibiotic?

${ }^{15}P_8 = A + 8 \cdot { }^{14}P_7 \Rightarrow A = $