Question

) Find the mean of 30 numbers .given mean of ten of them is 12 and the mean of remaining 20 is 9.

Answer 1

Hii 

First ten mean  is 12=12*10=120
Remaning 20 mean is 9=20*9=180
add the first ten mean product is 120 Reaming 20 mean product is180
                    120+180=300
30 number mean =30*x=300
                                    x=300/30=10
                   10 is the mean of 30numbers