A body cools from `50^(@)C` to `40^(@)C` in 5 min. The surroundings temperature is `20^(@)C`. In what further times (in minutes) will it cool to `30^(@)C` ?

Options

A. 5
B. `15/2`
C. `25/3`
D. 10

Answer

C

Explanation

Applying, `(T_(1)-T_(2))/t = alpha[(T_(1)-T_(2))/2-T_(0)]` two lines we have,
or `(50-40)/5 = alpha[(50+40)/2 - 20]`.............(i)
and `(40-30)/t = alpha[(40+30)/2-20]`..............(ii)
Solving these two equations, we get
`t = 25/3min`