Here is the question:
I have posted a link there to this topic so the OP can find my work.First order differential equation problem...?
rate of change of temperature between an object and its surrounding medium is proportional to the temperature difference. A hot coal of 160 degree celsius is immersed in water of 5 degree celsius. After 40 seconds, the temperature of coal is 70 degree celsius. Assume water is kept at constant temperature. Find
(a) the temperature of coal after 1 minute
(b) When does the temperture of coal reach 20 degree celsius