Finding the {f}_{i}{x}_{i}&{f}_{i}{{x}_{i}}^{2} we get,

Now, from above table we get, ∑fixi=176
Now, finding xˉ=∑fi∑fixi=22176=8
Now, finding variance, we get,
σ2=N1∑fixi−2(xˉ)2
⇒σ2=221×2048−(8)2
⇒σ2=93.090964
⇒σ2=29.0909
⇒[σ2]=[29.0909]=29