During the break, several students left the lyceum and several came to it. As a result, the number of students in the lyceum after the break decreased by $10 \%$, and the share of boys among the students of the lyceum increased from $50 \%$ to $55 \%$. Did the number of boys increase or decrease?
Let there be $m$ boys before the break in the lyceum. Since this constituted $50 \%$ of the total number of students, there were $2 m$ students in total.

After the break, the number of students decreased by $10 \%$, so there were $2 m \cdot 0.9=1.8 m$ students left. Of these, boys made up $55 \%$, which is

$1.8 m \cdot 0.55=0.99 m$.

Since $m>0.99 m$, the number of boys has decreased.

## Answer

Decreased.