An empty LPG cylinder weighs 14.8 kg. When full, it weighs 29.0 kg and shows a pressure of 3.47 atm. In the course of use at ambient temperature, the mass of the cylinder is reduced to 23.0 kg. The final pressure inside the cylinder is _________ atm. (Nearest integer)
(Assume LPG to be an ideal gas)

We are given that the empty (tare) mass of the cylinder is $$14.8\ \text{kg}.$$

When the cylinder is completely filled with LPG its total mass becomes $$29.0\ \text{kg}.$$

Hence the initial mass of LPG present is obtained by simple subtraction:

$$m_1 \;=\; 29.0\ \text{kg} - 14.8\ \text{kg} = 14.2\ \text{kg}.$$

At this stage the gauge shows an initial pressure

$$P_1 = 3.47\ \text{atm}.$$

During usage the mass of the cylinder (shell + remaining LPG) falls to $$23.0\ \text{kg}.$$

Therefore the mass of LPG that still remains is

$$m_2 \;=\; 23.0\ \text{kg} - 14.8\ \text{kg} = 8.2\ \text{kg}.$$

We treat LPG as an ideal gas. The ideal-gas equation is first stated:

$$PV = nRT,$$

where  $$n = \dfrac{m}{M}$$  is the number of moles, $$m$$ is the mass of gas, and $$M$$ its molar mass. For a rigid steel cylinder, the volume $$V$$ is constant. The problem says the ambient temperature is unchanged, so $$T$$ is also constant. Hence, for two different states of the same gas in the same cylinder, the ratio

$$\dfrac{P}{n} = \dfrac{RT}{V}$$

remains fixed. Substituting $$n = m/M$$, we get

$$P = \dfrac{RT}{VM}\,m.$$

Everything in the prefactor $$\dfrac{RT}{VM}$$ is constant, so pressure is directly proportional to mass when temperature and volume stay fixed:

$$\dfrac{P_1}{P_2} = \dfrac{m_1}{m_2}.$$

We now substitute the numerical values:

$$P_2 = P_1 \times \dfrac{m_2}{m_1} = 3.47\ \text{atm} \times \dfrac{8.2\ \text{kg}}{14.2\ \text{kg}}.$$

First compute the mass ratio:

$$\dfrac{8.2}{14.2} = 0.57746\;(\text{approximately}).$$

Then multiply by the initial pressure:

$$P_2 = 3.47 \times 0.57746 = 2.0038\ \text{atm}\;(\text{approximately}).$$

Rounding to the nearest whole number, we have

$$P_2 \approx 2\ \text{atm}.$$

So, the answer is $$2$$.