Question

If the mean of 25 observation is 27 & each observation is decreased by 7,that will be the mew mean

Answer 1

Mean = sum of the quantity of observations/ frequency

Hence sum of observations = frequency x mean

The total sum = 25 x 27
                       = 675

if each observation is decreased by 7, then total decrease = 25 x 7
                                                                      =175

minus 175 from the first total sum to find the new total sum of the observation =  675 - 175
                    = 500
Hence the new total = 500
The new mean will be =  total / frequency
                                    = 500/25
                                    = 20
new mean is 20

Answer 2

Answer:    20

The answer is here...

     See the adjoining picture