Answer:
The answer to your question is below
Explanation:
People need to know how to convert units because variables are measured in different units and it is necessary to know the equivalence to know if people is talking about the same thing.
For example, if we measure our height in feet and somebody measure his height in meters, we need to know how to convert units to know the exact height of this person.
Or if our currency is dollar and we travel to a country with a different currency, we must know how to convert units to know the price of something in a different country.