Given, 3 boys and 2 girls stand in a queue.

Sample space $$n(s)=\left| \!{\underline {\, {5} \,}} \right.=120$$

According to the given condition, following cases may arise.

BGGBB $$\quad \left| \!{\underline {\, {3} \,}} \right. \left| \!{\underline {\, {2} \,}} \right.$$

GGBBB $$\quad \left| \!{\underline {\, {3} \,}} \right. \left| \!{\underline {\, {2} \,}} \right.$$

GBGBB $$\quad \left| \!{\underline {\, {3} \,}} \right. \left| \!{\underline {\, {2} \,}} \right.$$

GBBGB $$\quad \left| \!{\underline {\, {3} \,}} \right. \left| \!{\underline {\, {2} \,}} \right.$$

BGBGB $$\quad \left| \!{\underline {\, {3} \,}} \right. \left| \!{\underline {\, {2} \,}} \right.$$

So, number of favorable ways $$=5\left| \!{\underline {\, {3} \,}} \right. \left| \!{\underline {\, {2} \,}} \right.=60$$

Required probability $$=\frac{60}{120}=\frac{1}{2}$$