A bullet travelling at a velocity of 10metres per second hits a plank of thickness 10g. calculate the velocity of the bullet if it has to pass through 10 such planks.

Please let me know the concept which I have to take to solve this problem.

There is insufficient information to allow a prediction.

10 m/s is a speed typical of a fast runner, not a bullet.

10 g is not a measurement of thickness.

You don't say if the "bullet" passes through a single plank or not, and with what amount of momemtum or eneergy loss.

Make sure you have copied the problem correctly. It makes no sense as it stands.