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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So, here you have to look at the periodic table and see what the molar mass of each molecule composing the water compound

its two hydrogen atom plus an oxygen molecule, making it about 18g per mol.
That said, looking at the mass, we have to ask ourselves, if a mol of water contains 18g of mass, how many moles do we have in 0.5g of water?
We just do a cross multiplication:
9514 1404 393
Answer:
x = 31
Step-by-step explanation:
The sum of angles in a triangle is 180°.
98° +51° +x° = 180°
x° = 31° . . . . . . . . . . . . subtract 149°
x = 31
Use a half-angle identity to find the exact value of sin pi/8