Two radioactive materials A and B have decay constants $10 \lambda$ and $\lambda$, respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of $A$ to that of $B$ will be $1/e$ after a time:\\
(1) $\frac { 1 } { 10 \lambda }$\\
(2) $\frac { 1 } { 9 \lambda }$\\
(3) $\frac { 1 } { 11 \lambda }$\\
(4) $\frac { 11 } { 10 \lambda }$