Answers

2016-02-28T22:05:03+05:30
20observation+10observation =15+30 so the mean of all observation 30is 45
1 5 1
thanks and r u sure about ur ans
yes I am sure
2016-02-28T22:18:27+05:30
My idea (may be right or wrong)
mean = sum of observations / total number of observations
lets consider sum of observations to be x
so mean = x/20
15=x/20
=300
next mean = x/10
30 = x/10
=300
mean =300 /30=10
orĀ 
900/30=30
1 5 1
thanks but now i m confused which is the correct
300+300=600 not 900
sry then mean = 20