Answer:
120960
Step-by-step explanation:
We get 11 books 7 of geography and 4 of chemistry
We need to line all of them with 2 constraints
1.-three of the geography must be: 1 in the middle and in each end, then we already have
C₄,₃ = 4! / ( 4 - 3 ) ! C₄,₃ = 4*3*2*1
C₄,₃ = 24 different ways
Now we have 7 books of chemistry. To place them we get
P₇ = 7! P₇ = 7*6*5*4*3*2*1 P₇ = 5040
Now the total number will be
C₄,₃* P₇ = 120960
(4x+9)(3x+5)
=12x^2+20x+27x+45
=12x^2+47x+45
20 has been added to the total of scores, so the new mean for the 20 scores will be 20/20 = 1 higher than it was.
The new population mean is 15+1 = 16.
