Question

100 mL at 250°K. Which proportion could you use to find the volume v of the gas if the temperature decreases to 150°K?

Answer 1

According to Charles' Law
V1 / T1 = V2 / T2
V2 = V1 * T2 / T1
V2 = 100 ml *150 / 250
V2 = 15,000 / 250
V2 = 60 ml
And to recheck that:
http://1728.org/charles.htm