The random variable X has the distribution B (n, 0.1). Given that the mean and standard deviation of X are equal, find the value of n. [5]

The only things I could work out were:

E(X)(mean) = n x 0.1

SD(X) = root of VAR(X)

VAR(X) = n x 0.1 x 0.9

VAR(X) = n x 0.09

n x 0.1 = root of 0.09 x n

What happens from here? Is it meant to be solved in a different way?