Answer:
0.45
Step-by-step explanation:
Divide 9 by 20.
This is a quadratic equation, i.e. an equation involving a polynomial of degree 2. To solve them, you must rearrange them first, so that all terms are on the same side, so we get

i.e. now we're looking for the roots of the polynomial. To find them, we can use the following formula:

where
is a compact way to indicate both solutions
and
, while
are the coefficients of the quadratic equation, i.e. we consider the polynomial
.
So, in your case, we have 
Plug those values into the formula to get

So, the two solutions are


35 divided by 573 is 0.0610820244328098
Probability that you will get exactly 4 tails, if you flip a fair coin 7 times is: 
Step-by-step explanation:
We need to find the probability that you will get exactly 4 tails, if you flip a fair coin 7 times.
This is the combination question.
The total combinations will be: 2^7=128
Now, finding number of ways we can get exactly 4 tiles:
We will use the formula:

in our given question, n= 7, k= 4
Putting values:

So, Probability that you will get exactly 4 tails, if you flip a fair coin 7 times is: 
Keywords: Probability
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