Correct Answer - `10.368 s`
Gain or loss in time due to thermal expansion
`Deltat = (1)/(2) xx Delta theta xxt xx alpha (alpha = (0.000036)/(3)//.^(@)C)`
`t =` duration time
`1day = 24 xx 3600 sec`.
`:. Deltat = (1)/(2) xx (0.000036)/(3) xx 20 xx 24 xx 3600`
`Deltat = 10.368 sec`.
Note: If we increase temperature then time period increases and watch becomes slow.