Yeah this is a human construction := I don't know how did Indians do this but now we are facingMaybe it's worth noting that mathematics is a human construct, an ideal. I once had a math exam question that could be answered numerically, say with 42. I was marked down for doing that, because the professor wanted the symbolic answer. To his way of thinking, using an actual number somehow dirtied the perfection.
Anyone that has worked in the real world knows that a calculated value with a long string of digits is absurd. You can't measure anything that precisely, and your accuracy may be off as well. Two significant figures is typical and more than three starts becoming very difficult.
There's a whole science of how to maintain proper significant figures when adding, multiplying, and averaging numbers. Any introductory text on analytical chemistry would cover it, and I'm sure you could find it in other sources as well.
The about symbol is used to explicitly note that a value has been rounded or approximated for practical reasons. For instance you might write that 3 x 3.3 is about 10. You wouldn't use the equals sign because it would not be technically correct.