If a variable is binomially distributed with n trials and a success probability of p, then the mean = np, variance = np(1–p) and standard deviation = square root of variance.
In this case, n = 1200, p = 0.35. So, mean = (1200)(0.35) = 420,
variance = (1200)(0.35)(1–0.35) = 273,
standard deviation = square root of variance = √273 = 16.52.
We can convert 7/10 to a decimal first.
7/10 = 0.7
Now we can multiply this problem easier.
35 x 0.7 = 24.5
Don’t go to that link it’s bad they trying to scam you
The square root of 141 =

This is because the two factors are 3 and 47, which both aren't perfect squares. You cannot take anything out.
If you want it simplified (like with a calculator) it would be: