Beats Questions

When two tuning forks (fork $1$ and fork $2$) are sounded simultaneously, $4$ beats per second are heard. Now, some tape is attached on the prong of the fork $2$. When the tuning forks are sounded again, $6$ beats per second are heard. If the frequency of fork $1$ is $200\text{ Hz}$, then what was the original frequency of fork $2$?

A tuning fork of known frequency $256\text{Hz}$ makes $5$ beats per second with the vibrating string of a piano. The beat frequency decreases to $2$ beats per second when the tension in the piano string is slightly increased. The frequency of the piano string before increasing the tension was:

Three sound waves of equal amplitudes have frequencies $(\nu -1)$, $\nu$, $(\nu +1)$. They superpose to give beats. The number of beats produced per second will be: