A metallic sphere cools from 500C to 400C in 300s. If atmospheric temperature around is 200C, then the sphere’s temperature after the next 5 minutes will be close to :

Newton's Law of Cooling,  θ1−θ2t1−t2=kθ1+θ22−θsur⇒50−40300=k50+402−20⇒10300=k45−20−−−1Now, 40−θf300=k40+θf2−20−−−−−2Dividing1 by 2, 1040−θf=2540+θf2−20⇒1040−θf=25θf×2⇒θf=1003=330C