Question 1183995
the possible arrangements, without any restrictions, are 5! = 120.
if the boys need to be together, that can happen in 3! arrangements = 6.
if the girls need to be together, that can happen in 2! arrangements = 2.
that would be a total of 6 * 2 = 12 possible arrangements if all the boys are on the left and another total of 2 * 6 = 12 possible arrangements if all the girls are on the left.
you get 24 possible arrangements out of 120 possible arrangements, giving you a probability of 24/120 = 1/5.


let the boys be 1,2,3.
let the girls be a,b.


when the girls are on the left, you get:


ab123
ab132
ab213
ab231
ab312
ab321

ba123
ba132
ba213
ba231
ba312
ba321


that's a total of 12.


when boys are on the left and the girls are on the right, that's another 12 possible arrangements, for a total of 24 out of 120 = 1/5.


as far as i can tell, the probability is 1/5.