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Maths Puzzle
Numerical Ability
Clocks and Calendars
At what time between 7 and 8 o'clock will the hands of a clock be in the same straight line but, not together?
A)5 min. past 7 B)5(2/11) min. past 7
C)5(3/11) min. past 7 D)5(5/11) min. past 7
Read Solution (Total 7)
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- D)5(5/11) min. past 7
When the hands of the clock are in the same straight line but not together, they are 30 minute spaces apart.
At 7 o'clock, they are 25 min. spaces apart.
Minute hand will have to gain only 5 min. spaces.
55 min. spaces are gained in 60 min.
5 min. spaces are gained in 5(5/11) min. - 12 years agoHelpfull: Yes(8) No(5)
- Please help me... I cant understand this....
- 12 years agoHelpfull: Yes(5) No(3)
- Ans. D) 5(5/11)min. past 7
At 7 o'clock the minute hand and hour hand are 210 degrees apart.
Now we have to bring both hands of clock close by 30 degrees.
in one minute, hour hand moves 1/2 degrees and minute hand moves 6 degrees.
So difference between minute hand and hour hand in 1 minute = 6 - 1/2 = 11/2 degrees.
After 7 o'clock, in one minute both hands will become close by 11/2 degrees.
Hands will come close by 30 degrees in = 30 * (2/11)g= 5(5/11)minutes and both hands will be in a straight line.
Thus at 5(5/11) min. past 7 the hands will be in straight line.
- 12 years agoHelpfull: Yes(4) No(2)
- if two hands will be on same straight line if they are 30 min apart
so 7'oclock two hands will 25 min apart
min hand has to gain more 5 min,
generally min hand gains 55 min in 1 hour over hours hand
so (60/55)*5=5(5/11) - 12 years agoHelpfull: Yes(3) No(3)
- at 5(5/11) min. past 7 , the hands of a clock will be in the same straight line but, not together.
- 12 years agoHelpfull: Yes(3) No(0)
- The answer should be D
Between A and B hours the angle between the hands of a clock is x at
(30A-x)(2/11) min past A
or
(30A+x)(2/11) min past A
as they are in same straight line and opposite in direction the angle should be x = 180
hence (30(7)-180)(2/11) min past 7 = (60/11) min past 7
i.e. 5 5/11 min past 7 it will happen,
and in any one hour time 180 will occur only once.
if we check for other case
(30(7)+180)(2/11) min past 7
(780/11) min past 7
i.e. 70 10/11 min past 7 meas it occurs at 8.10 10/11 min. - 12 years agoHelpfull: Yes(1) No(2)
- In this case try this rule (5x-30)*12/11 (here x stands for 7)
- 8 years agoHelpfull: Yes(0) No(0)
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