CAT 2018 Question Paper Shift 2 Solved Paper

Among a group of n persons, number of matches played $=\mathit{n}\left(\mathit{n}-1\right)/2$
Among the Junior participants, let the number of girls be $\mathit{n}$.
The number of matches played among girls
$=\mathit{n}\left(\mathit{n}-1\right)/2=153$
Number of boys $=43-18=25$
The number of matches played between a boy and a girl $=25\times 18=450$
Among the Senior level participants, let the number of boys be $\mathit{n}$.
The number of matches played between two boys
$=\mathit{n}\left(\mathit{n}-1\right)/2=276$
The number of girls $=51-24=27$
The number of matches played between a boy and a girl $=27\times 24=648$
Required answer $=450+648=1098$