A pan filled with hot food cools from 940C to 860C in 2 min. When the room temperature is at 200C, the time taken to cool from 710C to 690C is

From the Newton's law of cooling,θ1−θ2t∝θ1+θ22−θ0where, θ0 = temperature of surrounding∴ 94−86t1∝94+862−208t1∝(70)                    …(i)and   71−69t2∝71+692−202t2∝50    …(ii)On dividing Eq (i) by Eq (ii), we gett2t1=7050×4⇒t2=70×250×4⇒ t2=0.7min⇒t2=42s