In a survey, it was found that 40% people use petrol, 35% use diesel and remaining use CNG for their vehicles. Find the probability that a person chosen at random uses CNG.
Which fuel out of the above three is appropriate for the welfare of the society ?

Answer

To solve the problem step by step, we will first calculate the percentage of people using CNG and then find the probability of randomly selecting a person who uses CNG. Finally, we will discuss which fuel is more appropriate for the welfare of society.

### Step 1: Calculate the percentage of people using CNG
- We know that 40% of people use petrol and 35% use diesel.
- To find the percentage of people using CNG, we subtract the percentages of petrol and diesel users from 100%.

\[ \text{Percentage of CNG users} = 100\% - (\text{Percentage of petrol users} + \text{Percentage of diesel users}) \]

\[ \text{Percentage of CNG users} = 100\% - (40\% + 35\%) = 100\% - 75\% = 25\% \]

### Step 2: Find the probability that a person chosen at random uses CNG
- The probability of an event is calculated as the ratio of the number of favorable outcomes to the total number of outcomes.
- Here, the favorable outcome is the percentage of CNG users, which is 25%, and the total percentage is 100%.

\[ \text{Probability of using CNG} = \frac{\text{Percentage of CNG users}}{\text{Total percentage}} = \frac{25\%}{100\%} \]

\[ \text{Probability of using CNG} = \frac{25}{100} = \frac{1}{4} \]

### Step 3: Determine which fuel is appropriate for the welfare of society
- Among petrol, diesel, and CNG, CNG is generally considered more environmentally friendly as it produces fewer emissions compared to petrol and diesel. Therefore, for the welfare of society, CNG is the more appropriate fuel choice.

### Final Answers:
1. The probability that a person chosen at random uses CNG is \(\frac{1}{4}\).
2. CNG is the most appropriate fuel for the welfare of society.

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