The average time that a light bulb burns before it fails is 1000 hours. The probability that this light bulb burns between 100 and 1000 hours before failure is:____. (3 decimal places)
$$λ = \frac{1 \ \text{failure}}{1000 \ \text{hours}}$$ $$Pr(100<X<1000) =\int_{100}^{1000} \ \frac{1}{1000}e^{- \frac{1}{1000}x}\ \, dx = 0.536957...$$
The correct answer however is $0.0537$ and I have no idea as to how they got that answer and why the correct answer = $Pr(100<X<1000) / 10 $