Discuss the short cut method of calculating arithmetic mean

Short cut method : The calculation of mean by short cut method involves following steps:
(i) Any figure may be taken as an assumed mean of data.
(ii) Deviations of variable X, from the assumed mean taking into account with signs + or -.
(iii) The deviations are added and total is denoted by ‘Σdx’.
(iv) To calculate mean we put the formula : X =A + Σdx/N