Normal Distribution, probability that X differs from expected value by less than 10%

Question

I have a normal approximation of binomial, $X\sim \mathcal{N}(36,4.6475)$. I have to find the probability that the number of red blocks ($\mu = 36$) differs from its expected value by less than $10\%$. I know how to calculate normal distribution, I just don't understand how exactly I should work with these percentages and expected value?

Heeeelp. I tried calculating it between 32.4 and 39.6 But it should be between 32.5 and 39.5 why is that?

Answer 1

Hint:

To be found is $P\left[\left|X-36\right|<3.6\right]$ since $X$ differs from its expectation by less than 10% iff $\left|X-36\right|<3.6$.