Aptitude - Clock - Discussion
Discussion Forum : Clock - General Questions (Q.No. 7)
7.
At what time between 5.30 and 6 will the hands of a clock be at right angles?
Answer: Option
Explanation:
At 5 o'clock, the hands are 25 min. spaces apart.
To be at right angles and that too between 5.30 and 6, the minute hand has to gain (25 + 15) = 40 min. spaces.
55 min. spaces are gained in 60 min.
| 40 min. spaces are gained in |  |
60 | x 40 |  min |
= | 43 | 7 | min. |
| 55 | 11 |
 Required time = 43 |
7 | min. past 5. |
| 11 |
Discussion:
76 comments Page 1 of 8.
Bala said:
1 decade ago
How (25+15) is written? Plse explain it clearly.
Nitesh Nandwana said:
1 decade ago
@Bala.
Bala it is very simple.
For right angle we need 90 degree between hour hand and minute hand.
So here we are looking for that condition.
Now look at hour hand on 5 o'clock, you'll get that minute hand should be at 5. 40 to form right angle.
(90 degree between hour and minute hand).
Now move minute hand to 25 min, now minute hand and hour hand are together (forms 0 degree).
Now simply move 15 min more to form right angle.
Don't think why it is "25+15", think we need 40 to form right angle, consider on logic instead of calculation.
Bala it is very simple.
For right angle we need 90 degree between hour hand and minute hand.
So here we are looking for that condition.
Now look at hour hand on 5 o'clock, you'll get that minute hand should be at 5. 40 to form right angle.
(90 degree between hour and minute hand).
Now move minute hand to 25 min, now minute hand and hour hand are together (forms 0 degree).
Now simply move 15 min more to form right angle.
Don't think why it is "25+15", think we need 40 to form right angle, consider on logic instead of calculation.
Reddilavan said:
1 decade ago
There is a formula for finding time nd degree
ie angle=(11/2)*min-30*hr
in this problem the hr nd min hands should be in right angle that means angle=90 then we can find min
90=(11/2)*min-30*5
min=(90+150)*(2/11)
=43 7/11 ie 5hrs 43 7/11min
ie angle=(11/2)*min-30*hr
in this problem the hr nd min hands should be in right angle that means angle=90 then we can find min
90=(11/2)*min-30*5
min=(90+150)*(2/11)
=43 7/11 ie 5hrs 43 7/11min
(6)
Priya said:
1 decade ago
@Reddilavan
THANK U
THANK U
Nagaraj said:
1 decade ago
@red:how u got tis formula!!!
Prasad said:
1 decade ago
@Reddilavan
The formula you provided is Master formula. It works on almost all kind of problems of clock to find angle between the clock hands. Just take care of angle while choosing.
The formula you provided is Master formula. It works on almost all kind of problems of clock to find angle between the clock hands. Just take care of angle while choosing.
Abhishek said:
1 decade ago
@Reddilavan
It seriously a gud formula... we would be obligeed if we have more such formulae from your end.
It seriously a gud formula... we would be obligeed if we have more such formulae from your end.
Chandra shekar said:
1 decade ago
How did you get the fraction 60/55 in the above the calculation ?
Shree said:
1 decade ago
Hey in some prob we are using theta=30h-11m/2 and here reddilavan has mentioned theta=11m/2-30h. How we knew in which prob which formula must be used na? Can any one explain me.
Akki said:
1 decade ago
@Reddilavan how you got 90degree angle
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