Question

When it is 4:00 a.m. in Halifax, it is 1:00 p.m. in Karachi, and when it is 9:00 a.m. in Karachi, it is 5:00 a.m. in Warsaw. Mary left Halifax to fly to Karachi, but she accidentally left her watch on Warsaw time. According to Mary’s watch, she left Halifax at 9:40 p.m. on Monday. The local time when she arrived at Karachi was 3:00 p.m. Tuesday. How long was Mary’s flight?
a.
9 hours, 20 minutes
b.
13 hours, 20 minutes
c.
14 hours, 20 minutes
d.
17 hours, 20 minutes

Answer 1

Halifax → Karachi: +9 hours (4:00 Halifax = 13:00 Karachi).
Karachi → Warsaw: −4 hours (9:00 Karachi = 5:00 Warsaw).
So Warsaw = Halifax +5.

Her watch (Warsaw) read 21:40 Monday, so Halifax departure = 21:40 − 5h = 16:40 Monday.
That is 16:40 Halifax = 01:40 Tuesday Karachi. Arrival was 15:00 Tuesday Karachi.
Flight time = 15:00 − 01:40 = 13 hours 20 minutes.

Answer: b. 13 hours, 20 minutes.