We have, 5 boys and 5 girls.
Since, all the girls are sitting together, we consider them as one. Now, we can arrange 5 boys and 1 girl in 6! ways and these 5 girls (whom we considered as one) can also be arranged in 5! ways.
∴ Favorable number of ways = 6!5!
and total number of ways to arrange 5 boys and 5 girls = 10!
∴ Required probability 6!5!/10! = 1/42
