Answer
234.5 sec.
Work Step by Step
$Q_{1}$ is the value where $\frac{1}{4}=25$ % of the values are smaller than $Q_{1}$. 25% of the data here is: $24\cdot0.25=6$, therefore $Q_{1}$ is the average of the 6th and 7th value, which is (234+235)/2=234.5 sec..