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Question
Air is an important inexhaustible natural resource. It is essential for the survival of human beings, microbes, plants, and animals. The following table shows the percentage of various gases in the air.
| Contents of air | Percentage (by volume) |
| Nitrogen | 78 |
| Oxygen | 21 |
| Other (carbon dioxide, inert gases, water vapours, etc.) | 1 |
If a certain quantity (by volume) of air contains 4,200 litres of oxygen, find the total quantity of air taken and the amount of nitrogen in it.
Solution
Nitrogen in air = 78%, Oxygen = 21%, Others = 1%
If the air contains 4200 litres of oxygen, then the total quantity of air
= `(4200xx100)/21` litres
= 200 × 100 litres
= 20000 litres
and the amount of nitrogen in it = 20000 of 78%
= `20000xx78/100`
= 15600 litres
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