A beaker full of hot water is kept in a room. If it cools

A beaker full of hot water is kept in a room. If it cools from 80°C to 75°C in t₁ minutes, from 75° C to 70°C in t₂ minutes and from 70°C to 65°C in t₃ minutes, then

Let θ₀ be the temperature of the surrounding. Then

	80 - 75	= k		80 + 75	- θ₀
	t₁			2

Or,	5	k(77.5 - θ₀)
	t₁

Or, t₁ =	5	..........(i)
	k(77.5 - θ₀)

Similarly, t₂ =	5	..........(ii)
	k(72.5 - θ₀)

and, t₃ =	5	..........(iii)
	k(67.5 - θ₀)

From (1), (2) & (3), it is obvious that
t₁ < t₂ < t₃