Question

If the mean of 5 observation s x,x+1,x+2,x+4,x+6,x+8 is 11,find the mean of first three observatios.

Answer 1

mean of 5 observations=11
mean=sum of all observations÷number of observations
11=x+x+2+x+4+x+6+x+8÷5
11=5x+20÷5
11×5=5x+20
55=5x+20
55-20=5x
35=5x
35/5=x
7=x


So=> x=7

mean of first three observarions=x+x+2+x+4÷3
=3x+6÷3
=x+2
=7+2
=9


Hope this helps you......
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