1. Find the variance and standard deviation of the data given below class class 11-20 21-30 31-40 41-50 51-60 61-70 f 3 7 17 12 19 5

2. The mean weight of 150 students is 60kg.The mean weight of buys is 70kg with standard deviation of 10kg For the girls, the mean weight is 55kg and standard deviation of 15kg. Find the number of boys.​