A child received a balloon filled with 2.30 L of helium from a vendor at an
amusement park where the pressure in the balloon is 923 torr. What will the final
pressure of the balloon be, in torr, when the child uses some of the helium and
causes the final volume to fall to 1.55 L? Assume that the temperature is held
constant.

Answer : The final  pressure of the balloon will be, 1369.6 torr

Explanation :

Boyle's Law : It is defined as the pressure of the gas is inversely proportional to the volume of the gas at constant temperature and number of moles.

or,

where,

= initial pressure = 923 torr

= final pressure = ?

= initial volume = 2.30 L

= final volume = 1.55 L

Now put all the given values in the above equation, we get:

Thus, the final  pressure of the balloon will be, 1369.6 torr