Aptitude - Clock - Discussion

In 3 MIN = The clock gains 5 sec.
in 60 min(3 * 20) = clock gains 100 sec(5 * 20)
= i.e 100/60 min
= 5/3 min
So , If correct clock shows 1 hour=den da wrong clock shows 1 hr 5/3 min..
i.e
1 hr=1 hr 5/3 min
=1 * 5/(3*60) hour (convert to hour)
=37/36 hour

But we need to do reverse..
i.e
37/36 hrs(in wrong clock) = 1 hr
1 hour in wrong clock = 1/(37/36)=36/37 hr

9hr 15min=37/4 hrs

So
37/4 hours in wrong clock =36/37 * 37/4
= 9
So 7 a.m + 9 hrs= 4 pm ....

I hope every1 got it...

From 7am to 4:15pm the time traveled will be 9 hours and 15 min.
So in minutes it will be (9*60)+15=540+15=555
After every 3 min the clock will add 5 second,so in 555 min no of
seconds that will be added=(555/3)*5=925 seconds=925/60min=15min and 25sec
so the correct time will be=CURRENT TIME(that is 4:15pm)-(15min and 25 sec)
=3:59:35pm
35 seconds in min-->35/60=7/12min
so the correct answer must be 59(7/12) which is ""A""

[But this is wrong, read Sundar's explanation given below]

As given in question we know that.

A watch gains 5 seconds in 3 minutes.

Its means covert 3 min into seconds 4.

(3 x 60) = 180 sec (1 min = 60 sec).

Question tells 5 seconds gain.

It means for 180 sec it will become 180 + 5 = 185 seconds.

Right time is 180 seconds wrong time is 185 seconds.

Difference between true time and wrong time is 7 am to 4. 15 pm is 9 hours 15 min.

(9 x 60 = 540 + 15 = 555 min).

For 180 - 185.

? - 555.

(180 x 555) /185 = 540 in sec convert into min I. E 540/60 = 4 min.

THE CORRECT ANSWER IS OPTION(A)

Step 1: Find total gain per minute

Given: 5 sec gain in 3 min
Gain per minute = 5/3 sec

Step 2: Find total time shown by watch
From 7:00 a.m. to 4:15 p.m. = 555 minutes

Step 3: Find total gain in that time,
Total gain = 555 × 5/3.
= 925 sec.

Convert:
925 sec = 15 min 25 sec.

Step 4: Subtract gain from shown time,

Watch is fast, so:
Real time=4:15−15 min 25 sec.
= 3:59:35 p.m.
converting to mixed fraction give us answer as 3:59:35/60 that is equals to 3:59:7/12.

3min 5sec = 3min.
6min 10sec = 6min.

Similary 1hr = 1hr 1min 40sec.

Calculation:

6*10min = 6*10min 10*10sec
60 min = 60 min 100 sec(61min 40 sec)
So, total gain 1hour = 1min 40 sec.

Time between 7 am to 4.15 pm= 9hr 15 min.

In 9hr 15 min time gain will we 15min because;

9*1min 40 sec=> 9min + 360sec =>9 min + 6min =>15min.

So the correct time in the clock is 4 pm.

And gain in remaining 15 min =25sec (5*5).

25 sec can be neglected.

Hence the correct answer option B.

3min 5sec = 3min.
6min 10sec = 6min.

Similary 1hr = 1hr 1min 40sec.

Calculation:

6*10min = 6*10min 10*10sec
60 min = 60 min 100 sec(61min 40 sec)
So, total gain 1hour = 1min 40 sec.

Time between 7 am to 4.15 pm= 9hr 15 min.

In 9hr 15 min time gain will we 15min because;

9*1min 40 sec=> 9min + 360sec =>9 min + 6min =>15min.

So the correct time in the clock is 4 pm.

And gain in remaining 15 min =25sec (5*5).

25 sec can be neglected.

Hence the correct answer option B.

Time from 7 a.m. to 4.15 p.m. = 9 hrs 15 min. = 37/4 hrs.

3 min. 5 sec. of this clock = 3 min. of the correct clock.

37/720hrs of this clock = 1 /20hrs of the correct clock.
(Convert into hours in both sides).

(37/720)x 1 hrs of this clock = 1 /20hrs of the correct clock.

1 hrs of this clock = (1 /20)* (720/37) hrs of the correct clock.

(37/4) hrs of this clock = (1 /20)* (720/37)*(37/4) hrs of the correct clock.
i.e. = 9 hrs.

i.e. The correct time of the clock is 4 p.m.

Given->
for 185 seconds of wrong time 180 seconds is correct time;
So 33300 seconds of wrong seconds what will be the correct seconds?

Surely its 180*33300/185 ie 32400 seconds. ie 9 hrs (32400/3600).

To get the correct time add 9 hrs to 7.00 am ie 4.00 pm
****************************************************************
How I got 33300 seconds ?

From 7.00 am to 4.15 pm its 9 hrs and 15 seconds ie 9*60*60 + 15*60 seconds =33300 seconds )

Is it simple ?

Hai friends,

I think we have to find the error.
Clock gains 5 sec in 180sec of actual clock.

So,

The error is 5 sec in 185 sec. in errored clock.
In error clock. The passed time is 9H and 15min.

Which is equal to 555 min.(9 * 60 + 15).
Thus it is 33300 in sec.

We have 5 sec error for every 185 sec.
So for 33300 sec we have 900 sec error. (33300 * 5/185).

Error in min. is 15 (900 sec / 60).

So the actual time is 4:00pm (4:15 - 15 min).

I hope you all understood.

Given in question that in every 3 minutes 5 sec = 185 sec. increases, so the wrong time we get 4:15.

Now we have to get the correct time, for this first take the wrong time.
Given it is 4:15 which is started from 7 in morning, so that's mean it is 9 hr 15 minutes.
555 min = 333000 sec.
Now for the correct clock,
It will be 3 minute = 180 seconds.

So, correct time can be written as (180/185)*333000 sec. = 32400 sec.
which is equal to 9 hr so the answer is 4 p.m.