Weighted average number of ordinary shares

[Bread & Butter]

I would greatly appreciate if anybody could explain how to calculate weighted average number of ordinary shares of a company;
Let say Company A had ordinary shares at end of 2547 = 100 shares and Q1, Q2, Q3, Q4 of 2548 equal to 110, 120, 130 and 140 shares respectively.
My question is what is weighted average number of ordinary shares of Company A at end of Q1, Q2, Q3 and Q4 of 2548 ?

Thanks