Aptitude - Clock
6.
The reflex angle between the hands of a clock at 10.25 is :
Answer
Angle traced by hour hand in 12 hours = 360°
∴ Angle traced by hour hand in 10 2560 hrs i.e. 12512 hrs =
360°12 x 12512 
= 312.5°
Angle traced by hour hand in 60 min. = 360°
∴ Angle traced by hour hand in 25 min. = 360°60 x 25 = 150°
Reuired angle = 360° − {312.5° − 150°} = 360° − 162.5° = 197.5°
Answer :
Option DExplanation :
Angle traced by hour hand in 12 hours = 360°
∴ Angle traced by hour hand in 10 2560 hrs i.e. 12512 hrs =
360°12 x 12512 = 312.5°Angle traced by hour hand in 60 min. = 360°
∴ Angle traced by hour hand in 25 min. =
360°60 x 25 = 150° Reuired angle = 360° − {312.5° − 150°} = 360° − 162.5° = 197.5°
7.
How many times in a day, are the hands of a clock in straight line but opposite in direction ?
Answer
The hands of a clock point in opposite directions (in the same straight line) 11 times in every 12 hours. (Because between 5 and 7 they point in opposite directions at 6 o'clcok only).
So, in a day, the hands point in the opposite directions 22 times.
Answer :
Option BExplanation :
The hands of a clock point in opposite directions (in the same straight line) 11 times in every 12 hours. (Because between 5 and 7 they point in opposite directions at 6 o'clcok only).
So, in a day, the hands point in the opposite directions 22 times.
8.
How much does a watch lose per day, if its hands coincide every 64 minutes ?
Answer
55 min. spaces are covered in 60 min.
∴ 60 min. spaces are covered in = 6055 x 60min. = 65 511 min.
Loss in 64 min. =65 511 − 64 = 1611 min.
Loss in 24 hrs = 1611 x 164 x 24 x 60 min. = 32 811 min.
Answer :
Option AExplanation :
55 min. spaces are covered in 60 min.
∴ 60 min. spaces are covered in =
6055 x 60min. = 65 511 min. Loss in 64 min. =
65 511 − 64 = 1611 min.Loss in 24 hrs =
1611 x 164 x 24 x 60 min. = 32 811 min. 9.
A watch which gains uniformly is 2 minutes low at noon on Monday and is 4 min. 48 sec fast at 2 p.m. on the following Monday. When was it correct ?
Answer
Time from 12 p.m. on Monday to 2 p.m. on the following Monday = 7 days 2 hrs = 170 hrs.
∴ The watch gains2 + 4 45 min. or 345 min. in 170 hrs.
Now, 34 5 min. are gained in 170 hrs.
∴ 2 min. are gained in170 x 2 x 534 hrs = 50 hrs.
∴ Watch will be correct 2 days 2 hrs. after 12 p.m. on Monday i.e., it will be correct at 2 p.m. on Wednesday.
Answer :
Option BExplanation :
Time from 12 p.m. on Monday to 2 p.m. on the following Monday = 7 days 2 hrs = 170 hrs.
∴ The watch gains
2 + 4 45 min. or 345 min. in 170 hrs. Now, 34 5 min. are gained in 170 hrs.
∴ 2 min. are gained in
170 x 2 x 534 hrs = 50 hrs.∴ Watch will be correct 2 days 2 hrs. after 12 p.m. on Monday i.e., it will be correct at 2 p.m. on Wednesday.
10.
How many times in a day, the hands of a clock are straight ?
Answer
In 12 hours, the hands coincide or are in opposite direction 22 times.
∴ In 24 hours, the hands coincide or are in opposite direction 44 times a day.
Answer :
Option CExplanation :
In 12 hours, the hands coincide or are in opposite direction 22 times.
∴ In 24 hours, the hands coincide or are in opposite direction 44 times a day.
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