UPSC 2015 CDS I Math Paper

Angle formed by the hour hand in

17

2

‌hours=

360°

12

×

17

2

=255°
Angle formed by the minute hand in 30 minutes =

360°

60

×30=180°
Therefore, angle formed by the hour hand and minute hand at 8:30=255°–180°=75°
Alternative Method:
We have
n=8,t=30
{30(n−

t

5

)+

t

2

}°
∴ Required angle = 75°
={30(8−

30

5

)+

30

2

}°
=[30(8−6)+15]°
=(60+15)°=75°