Question

The mean of six observations is 10. If the mean of four observations is 12.5, then what is the mean ofthe remaining two observations?

pls tell fast

Answer 1

Answer:

The sum of firs 6 numbers is 

=15×6

=90

Therefore

x1+x2+...x6=90 ...(i)

And 

The sum of last five number is 

=10×5

=50

Therefore

x10+x9+x8...x6=50 ...(ii)

Sum of all number is 

=12.5×10

=125 ...(iii)

Hence

i+ii

=140

=(x1+x2+....x10)+x6

=125+x6

Or 

x6=15.

Answer 2

Question :

The mean of six observations is 10. If the mean of four observations is 12.5, then what is the mean ofthe remaining two observations ?

Solution :

The sum of firs 6 numbers is

=15×6

=90

Therefore x1 + x2 +...x6 = 90 ...(i)

And

The sum of last five number is

=10×5

=50

Therefore x10 + x9 + x8 + ...x6 = 50 ...(ii)

Sum of all number is

=12.5×10

=125 ...(iii)

Hence

On Adding (i) + (ii) = 140

=(x1 +x2 +....x10) +x6 = 125+x6

Or

x6 = 15.