Why to take always RL of BM as 100.000?

Question

Why to take always Reduced Level of Benchmark as 100.000?

Answer 1

Its not necessary. But it helps in the calculations. After doing all the calculations, you can directly say that the last station is a certain meter higher or lower elevation with respect to the BM without any calculation.
That is why it is taken like that.You can try with some other no also.