Two tuning forks when sounded together produce 5 beats in 2 seconds. The time interval between two successive maximum intensities of sound is

We know that beat is produced between 2 successive maximum intensities.

Time interval between successive Maximums is given by 
$\mathrm{t}=\frac{1}{\mathrm{N}}=\frac{1}{2.5}=0.4 \sec$