So you need to divide your answer by three than multiply by 5 and that would give you your answer
I'm not 100 percent sure but I think is e
Both the heads and tails will have a probability of 0.5 with a fair coin. ... TO find probability that foe the 7th toss head appears exactly 4 times.
This involves quite a lot of arithmetic to do manually.
The first thing you do is to make the first number in row 2 = to 0.
This is done by R2 = -3/2 R1 + R2
so the matrix becomes
( 2 1 1) ( -3 )
( 0 -13/2 3/2) (1/2 )
(5 -1 2) (-2)
Next step is to make the 5 in row 5 = 0
then the -1 must become zero
You aim for the form
( 1 0 0) (x)
(0 1 0) (y)
(0 0 1) ( z)
x , y and z will be the required solutions.
