Explanation:

The hour hand rotates 0.5° per minute while the minute hand rotates 6° per minute.
At exactly four, the hour hand as completed 240 minutes = 120°.
Hence angle between minute and hour hand at that point is 120°.
At 4:25, the minute hand has moved 25*6= 150°.
Thus angle between minute hand and 12(on the clock) is 150°.
But at the same time, even the our hand has moved 0.5*25= 12.5°.
Now, the angle between the hour hand and 12(on the clock) is 120+12.5=132.5°.
Now the angle between the two hands of the clock is 150°-132.5° = 17.5° .