Aptitude - Clock - Discussion
Discussion Forum : Clock - General Questions (Q.No. 4)
4.
A watch which gains 5 seconds in 3 minutes was set right at 7 a.m. In the afternoon of the same day, when the watch indicated quarter past 4 o'clock, the true time is:
Answer: Option
Explanation:
| Time from 7 a.m. to 4.15 p.m. = 9 hrs 15 min. = | 37 | hrs. |
| 4 |
3 min. 5 sec. of this clock = 3 min. of the correct clock.
 |
37 | hrs of this clock = | 1 | hrs of the correct clock. |
| 720 | 20 |
| |
37 | hrs of this clock = |  |
1 | x | 720 | x | 37 |  |
hrs of the correct clock. |
| 4 | 20 | 37 | 4 |
= 9 hrs of the correct clock.
The correct time is 9 hrs after 7 a.m. i.e., 4 p.m.
Discussion:
154 comments Page 3 of 16.
Shivam said:
9 years ago
@Dedeepya.
We can't go with the process you suggested because;
Let us take the correct time be 'x'.
Now as we already know that 'x' will be lesser than 4 : 15.
Now the mistake in your idea is you are taking x as 4:15 which means in another (4 : 15 - x) the error clock will gain (4 : 15 - x) * 3s, which you are not considering.
Kindly take 'x' instead of 4 : 15 and solve again you will definitely land into a correct answer.
We can't go with the process you suggested because;
Let us take the correct time be 'x'.
Now as we already know that 'x' will be lesser than 4 : 15.
Now the mistake in your idea is you are taking x as 4:15 which means in another (4 : 15 - x) the error clock will gain (4 : 15 - x) * 3s, which you are not considering.
Kindly take 'x' instead of 4 : 15 and solve again you will definitely land into a correct answer.
Praveen said:
1 decade ago
FAULT CLOCK CORRECT CLOCK
7am < ---------------- > 7am
8am 100 sec < ------------ > 8am
9am 200 sec < ------------ > 9am
So on..
4pm 900 sec < ------------ > 4pm
So 4pm 900 sec = 4pm 900/60 min = 4pm 15 min.
Therefore when Fault clock shows the time 4pm 15 min the Correct clock will show 4pm.
So correct answer is 4pm.
7am < ---------------- > 7am
8am 100 sec < ------------ > 8am
9am 200 sec < ------------ > 9am
So on..
4pm 900 sec < ------------ > 4pm
So 4pm 900 sec = 4pm 900/60 min = 4pm 15 min.
Therefore when Fault clock shows the time 4pm 15 min the Correct clock will show 4pm.
So correct answer is 4pm.
Pooja said:
1 decade ago
From 7 am to 4 pm, We are getting 900 sec gain, which is 900/60 = 15 min gain.
Now, the question has asked what will be the actual time when it is showing 4:15 pm.
Now, at 4 pm it already has gained 15 min, i.e. it is showing 4:15 pm already.
I was doing it wrong when I took 900 + 25 sec, where 25 sec was for 4 to 4:15 pm, which is wrong.
We are not asked to calculate time at 4:15 pm, we are asked for 4 pm.
Now, the question has asked what will be the actual time when it is showing 4:15 pm.
Now, at 4 pm it already has gained 15 min, i.e. it is showing 4:15 pm already.
I was doing it wrong when I took 900 + 25 sec, where 25 sec was for 4 to 4:15 pm, which is wrong.
We are not asked to calculate time at 4:15 pm, we are asked for 4 pm.
(1)
Pumpkin pieeeeee said:
7 months ago
The answer is A.
A lot of people are ignoring the extra 25 seconds.
The exact time gained is 925 seconds.
(This is best explained in the comment down below)
900 seconds is 15 minutes. So, we deduct 15 minutes from the time given.
ADDITIONALLY, 25 seconds also will be deducted -
60 - 25 = 35 seconds remaining.
Hence, 35/60 which explains the extra 7/12.
The final answer is -> 59 7/12 minutes past 3.
A lot of people are ignoring the extra 25 seconds.
The exact time gained is 925 seconds.
(This is best explained in the comment down below)
900 seconds is 15 minutes. So, we deduct 15 minutes from the time given.
ADDITIONALLY, 25 seconds also will be deducted -
60 - 25 = 35 seconds remaining.
Hence, 35/60 which explains the extra 7/12.
The final answer is -> 59 7/12 minutes past 3.
(18)
Sasi said:
1 decade ago
For 3 mins 5 sec gain.
i.e for 180 sec clock shows 185 sec.
That means for every hour it's shows 1 min 40 sec more than actual time.
We need to calculate actual time when clock shows 4:15 pm.
Given that time set at 7 am so the difference between 7 to 4:15 is 9:15 hours.
Clock showing us 1 min 40 secs more for every hour then for 9 hours 15 secs it shows 15 mins fast.
So the answer is 4 pm.
i.e for 180 sec clock shows 185 sec.
That means for every hour it's shows 1 min 40 sec more than actual time.
We need to calculate actual time when clock shows 4:15 pm.
Given that time set at 7 am so the difference between 7 to 4:15 is 9:15 hours.
Clock showing us 1 min 40 secs more for every hour then for 9 hours 15 secs it shows 15 mins fast.
So the answer is 4 pm.
Akhil said:
8 years ago
7am to 4.15pm.
Total 9hrs 15min.
Total time in min= 9*60+15=555min.
For every three min, 5 seconds will be added to the wrong clock
555min /3min= 185 times
So total second added 185*5=925sec,
now convert 925sec to min=925/60= 15 min 25 sec,
so the time in original clock will be 4pm.
555min-15min, =540min=9hrs.
25 sec is neglected because clocks trigger by 5sec only after completing 3mins.
Total 9hrs 15min.
Total time in min= 9*60+15=555min.
For every three min, 5 seconds will be added to the wrong clock
555min /3min= 185 times
So total second added 185*5=925sec,
now convert 925sec to min=925/60= 15 min 25 sec,
so the time in original clock will be 4pm.
555min-15min, =540min=9hrs.
25 sec is neglected because clocks trigger by 5sec only after completing 3mins.
Jeyam said:
9 years ago
@Aishwarya.
You don't get confused, first calculate how many minutes are there.
9hrs * 60 minutes +15 = 555 minutes.
Again calculate how many 3 minutes are there i.e. 555 ÷ 3 =183.
Again 180 minutes * 5 second = 915.
Again 914 ÷ 60 = 15 minutes. So 4 : 15 - 15 = 4pm.
Don't bother about the remaining 15 sec because we calculate ahead of the 15 minutes, so it's very factual to deduct.
You don't get confused, first calculate how many minutes are there.
9hrs * 60 minutes +15 = 555 minutes.
Again calculate how many 3 minutes are there i.e. 555 ÷ 3 =183.
Again 180 minutes * 5 second = 915.
Again 914 ÷ 60 = 15 minutes. So 4 : 15 - 15 = 4pm.
Don't bother about the remaining 15 sec because we calculate ahead of the 15 minutes, so it's very factual to deduct.
Kasinath@Hyd said:
1 decade ago
7am to 4:15====>is 9hrs and 15 min.
3min ====EXCEEDS===> 5sec.
15min==============> 25sec equation (1).
1hr (60min) =========> 100sec.
====================
======So on=========
====================
9hr=================> 900sec equation (2).
9:15 == equation(1)+equation(2) => 925 sec i.e. in 9:15 min time exceeded by 15 min.
Therefore time is 4 pm and not 4:15.
3min ====EXCEEDS===> 5sec.
15min==============> 25sec equation (1).
1hr (60min) =========> 100sec.
====================
======So on=========
====================
9hr=================> 900sec equation (2).
9:15 == equation(1)+equation(2) => 925 sec i.e. in 9:15 min time exceeded by 15 min.
Therefore time is 4 pm and not 4:15.
Meenu said:
1 decade ago
Hi Sundar...
Please help me out.. I did not understand after this step...
[9 hr 15 min = 555 min = 33300 sec]
33300 sec :: (180/185 x 33300) sec
33300 sec :: 32400 sec
333000sec = 9 hrs 15 min :: 32400 sec = 9 hrs [:. 32400/3600 = 9]
So,
Time passed by Error clock = 9 hrs 15 min.
Time passed by Original clock = 9 hrs.
Therefore, 9 hrs after 7 am is 4 pm.
Please help me out.. I did not understand after this step...
[9 hr 15 min = 555 min = 33300 sec]
33300 sec :: (180/185 x 33300) sec
33300 sec :: 32400 sec
333000sec = 9 hrs 15 min :: 32400 sec = 9 hrs [:. 32400/3600 = 9]
So,
Time passed by Error clock = 9 hrs 15 min.
Time passed by Original clock = 9 hrs.
Therefore, 9 hrs after 7 am is 4 pm.
Ankit said:
7 years ago
3: 5 Sec (wrong Clock) = 3 min ( Right Clock).
Now convert 3:5 Sec into min = 3+(5/60)== 37/12 min.
37/12 min will be === to 3 min of wrong clock.
1min of wrong clock will be = 3*12/37 = 36/37min of right clock.
9:15 min will be of wrong clock ==36/37*555 ( Total time trvel = 9:15min =555min) of right clock.
= 19980/37.
= 540min.
= 9 hrs = 4 PM.
Thanks.
Now convert 3:5 Sec into min = 3+(5/60)== 37/12 min.
37/12 min will be === to 3 min of wrong clock.
1min of wrong clock will be = 3*12/37 = 36/37min of right clock.
9:15 min will be of wrong clock ==36/37*555 ( Total time trvel = 9:15min =555min) of right clock.
= 19980/37.
= 540min.
= 9 hrs = 4 PM.
Thanks.
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