Question

The sub index values of NO$_2$, SO$_2$ and PM$_{10}$ are 80, 80 and 100, respectively. According to the National Air Quality Index (NAQI) released by the Government of India in the year 2015, the overall NAQI is:

• A. 80
• B. 260
• C. 100
• D. 151

Hint:

For NAQI, always take the \textbf{highest sub-index value} among all pollutants. Do not sum or average. The worst pollutant determines the index.

Answer 1

The Correct Option is C

Step 1: Recall the NAQI calculation rule.
The National Air Quality Index (2015) uses sub-indices for each pollutant (NO$_2$, SO$_2$, PM$_{10}$, PM$_{2.5}$, O$_3$, CO, NH$_3$, Pb, etc.). The overall NAQI is defined as the maximum of these sub-indices, not the average or sum. This is because the pollutant with the worst effect on health should decide the overall quality.
Step 2: Apply the given values.
- Sub-index for NO$_2 = 80$ - Sub-index for SO$_2 = 80$ - Sub-index for PM$_{10} = 100$
Step 3: Choose the maximum.
The overall NAQI = $\max(80, 80, 100) = 100$.
Step 4: Eliminate wrong options.
- Option (A) 80 → wrong, because not the maximum. - Option (B) 260 → wrong, because NAQI is not calculated by adding values. - Option (D) 151 → wrong, because NAQI is not calculated by averaging values. Therefore, the correct answer is 100. Final Answer: \[ \boxed{100} \]