If `overline x = 2.1` and `sum f_i = 25`, find `sum f_i x_i`

If sum f_i d_i =1885 and sum f_i=100 , then the value of bar d is...a) 1.885 b) 188.5 c) 18.85 d) 1885

The formula to find the mean deviation (bar d) in Assumed mean method is...a) (sum f_i d_i)/(sum d_i) b) sum f_i d_i c) (sum f_i d_i)/(sum f_i) d) (sum d_i)/(sum f_i d_i)

The formula to find mean by step deviation method is....a) (sum f_iu_i)/(sum f_i) b) A+ bar d c) A+g bar u d) ( sum f_i)/(sum f_i u_i)

If f(x) = 2x , then find f'(1).