Why is expressing numbers in scientific notation useful?
In the case of large values, it avoids the use of large numbers of trailing zeros or of long strings of non-zero digits when that level of accuracy is not required or simply spurious. Similarly, in the case of very small numbers, it avoids the use of large numbers of leading zeros. The long string of zeros makes it difficult to quickly judge orders of magnitudes and also helps avoid errors.
What is the distance from the earth to the Andromeda galaxy in scientific notation?
It is 2.4*1019 kilometres away.
What is three hundred forty two thousand in scientific notation?