Answer :
sum of observation = 640p +2800
no. of observation = 12p +60
mean=sum of observation / no. of observation
50 = 640p + 2800 / 12p +60
600p + 3000 = 640p + 2800
3000 - 2800 = 640p - 600p
200 = 20p
10 = p
no. of observation = 12p +60
mean=sum of observation / no. of observation
50 = 640p + 2800 / 12p +60
600p + 3000 = 640p + 2800
3000 - 2800 = 640p - 600p
200 = 20p
10 = p