13. statistics — MATHS STD 11 Science — Question

Four digits number which is divisible by $7$ are $1001,1008,1015, \ldots .$ $9996 .$

Hence, total number of such numbers $=1286$

$Median=\frac{\left(\frac{N}{2}\right)^{\text {th }} observatio+\left(\frac{N}{2}+1\right)^{\text {th }}\,observation}{2}$

$Median=\frac{\left(\frac{1286}{2}\right)^{\text {th }}\,observation+\left(\frac{N}{2}+1\right)^{\text {th }}\,observation}{2}$

$=\frac{643^{th}+644^{th}}{2}$

$=\frac{(1001+(642)7)+(1001)+(643)7)}{2}$

$=\frac{2(1001)+7(642+643)}{2}$

$=\frac{2(1001)+7(1285)}{2}$

$=1001+4497.5=5498.5$