Answer:
Step-by-step explanation:
Let T be the temperature of an object at time t , then
dT / dt will be rate of change of temperature
According to newton's law of cooling
dT / dt = k ( T - T₂ )
where T₂ is temperature of surrounding , T is temperature of object , k is a constant .
dT / dt = k ( T - T₂ )
Given k = .4 , ambient temperature T₂ = 68⁰C
dT / dt = .4 ( T - 68 )
dT / ( T - 68 ) = .4 dt .
This is required differential equation .