jmc

Using $d=rt$, we can set up an equation for when Jill arrives at the swimming pool: $1=10t$ Solving for $t$, we get that Jill gets to the pool in $\frac{1}{10}$ of an hour, which is $6$ minutes. Doing the same for Jack, we get that Jack arrives at the pool in $\frac{1}{4}$ of an hour, which in turn is $15$ minutes. Thus, Jill has to wait $15-6=\boxed{9}$ minutes for Jack to arrive at the pool.