The mean of a set of six numbers is 60. If the mean of the first five is 50, find the sixth number in the set.

walex4jesus

13 years ago

Note:let £=summation

A=mean of six nos,B=mean of five nos

£X6=summation of six nos and £X5=summation of five nos,Xn=nth term e.g X6=the sixth number

let solve

A=60,B=50

Recall:

mean=(£Xn)/n

therefore,A=£X6/6

but A=60

hence,60=£X6/6

cross-multiplying

£X6=250 i.e summation of d six set of number is 250

B=£x5/5

but B=50

50=£x5/5

cross-multiplying

£x5=250

i.e summation of the five number is 250

Recall:

Xn=£Xn-£X(n-1)

therefore,d six number=(sum of d six set of numbers) minus (sum of d first five numbers)

X6=£X6-£X5

X6=360-250

X6=110

i.e the six number=110

tyjesma

12 years ago

Funny@favOr

cosinfavor

13 years ago

very simple 60 + 50=100