Question

The arithmetic mean of 10 number s is 7.The arithmetic mean of 15 number s is 12.,then the mean of all observations is

Answer 1

Since avg is given for 10 numbers, therefore sum total of 10 number is =10×7=70
similarly for 15 numbers, sum total is =15×12=180
Hence the sum of all the observations is =180+70=250
Mean of all observations =(sum)/(number)
=250/(10+15)
=10