The speed the fan will turn is 625 rpm
Since they fan and the pulley ahve the same linear speed v = rω where
Then
r₁ω₁ = r₂ω₂ where
Making ω₁ subject of the formula, we have
ω₁ = r₂ω₂/r₁
Substituting the values of the variables into the equation, we have
ω₁ = r₂ω₂/r₁
ω₁ = 2 in × 1250 rpm/4 in
ω₁ = 1250 rpm/2
ω₁ = 625 rpm
So, the speed the fan will turn is 625 rpm
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