Two clocks are set right at 10 am. One gains 20 seconds

Two clocks are set right at 10 am. One gains 20 seconds and the other loses 40 seconds in 24 hours. What will be the true time when the first clock indicates 4 pm on the following day?

From 10 am to 4 pm on the following day = 30 hours
Now, 24 hours 20 seconds of the first clock = 24 hours of the current clock.

∴ 1 hour of the first clock =	^{24 x 180}	hours
	4321

∴ 30 hour of the first clock =	^{24 x 180 x 30}	hours
	4321

Now,	24 x 180 x 30	hours = 29 hours 59	2521	minutes
	4321		4321

∴ When the first clock indicates 4 pm on the following day the true time will be
3 hours 59 2521 minutes.
4321