Answer: There are 20 socks in the first case and there are 75 socks in the second case.
Step-by-step explanation:
Since we have given that
Number of equal groups = 5
Let the total number of socks be 's'.
According to question, expression will be
Now, Suppose number of socks in each group = 4
So, it will become,
Suppose number of socks in each group = 15
So, Total number of socks become
Hence, there are 20 socks in the first case and there are 75 socks in the second case.
Euler's formula tells us that


Suppose we subtract the two. This eliminates the cosine terms.

Divide both sides by

and you're done.
The probability the spinner lands on a prime number is 4/10 or 40%