For data -1, 1, 4, 3, 8, 12, 17, 19, 9, 11; if M is the median of first 5 observations and N is the median of last five observations, then what is the value of 4M - N ? 

Let P, Q, R represent mean, median and mode. If for some distribution $5 P=4 Q=\frac{R}{2}$ then what is $\frac{P+Q}{2 P+0.7 R}$ equal to ?

Let P be the median, Q be the mean and R be the mode of observations x_1, x_2, x₃, .....x_n. Let $S=\sum\limits_{i=1}^n\left(2 x_i-a\right)^2$ S takes minimum value, when a is equal to