Question

Average of seven number is 12. If average of first four number is 10 and last four numbers is 15

Answer 1

Let the numbers be a, b,c,...,g

A/Q

(a+b+...+g)/7=12

a+b+...+g=84. ---- i

Again,

(a+b+c+d)/4=10

a+b+c+d=40 ----ii

Again,

(d+e+f+g)/4=15

d+e+f+g=60 -------iii

ii+iii

a+b+c+d+d+e+f+g=40+60=100-----iv

iv - i

(a+b+c+d+d+e+f+g) - (a+b+c+d+e+f+g)

=100 - 84

d=16

The fourth number is 16.