Question

the mean of 5 observation is 40 the mean of four of them is 35. then 5th observation is ______
a. 50
b. 60
c. 70
d. 40

Answer 1

Answer:

Step-by-step explanation:

Mean = sum of obs. / Total obs.

40= sum of obs. /5

Sum of obs. = 40*5 = 200

Now, mean of 4 obs. is 35.

35= sum of obs. / 4

Sum of obs. = 35*4 = 140

5th obs. is 200-140 = 60

Answer 2

Answer:

Mean = sum of observation /total number of observation

Let x be the sum of the observation for mean of 5

So

Mean =40, total number of observation = 5

40=x/5

40X5= 200

Therefore x = 200

Let y be the sum of the observation for mean of 4

Mean = 35 ,total number of observation = 4

35=y/4

=35X 4

=140

So 200-140= 60

b) 60 is the correct answer

Hope it helps u buddy