11/5 in/hr
s = snow height (in)
t = time (hrs)
s = ¹¹/₅.t
2.5 = ⁵/₂
School closes when s > 2.5 or s > ⁵/₂
⁵/₂ = ¹¹/₅.t
⁵/₂ ÷ ¹¹/₅ = t
t = ⁵/₂.⁵/₁₁
= ²⁵/₂₂
School closes if t > ²⁵/₂₂
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