Aptitude - Problems on H.C.F and L.C.M - Discussion

Discussion Forum : Problems on H.C.F and L.C.M - General Questions (Q.No. 15)
15.
A, B and C start at the same time in the same direction to run around a circular stadium. A completes a round in 252 seconds, B in 308 seconds and c in 198 seconds, all starting at the same point. After what time will they again at the starting point ?
26 minutes and 18 seconds
42 minutes and 36 seconds
45 minutes
46 minutes and 12 seconds
Answer: Option
Explanation:

L.C.M. of 252, 308 and 198 = 2772.

So, A, B and C will again meet at the starting point in 2772 sec. i.e., 46 min. 12 sec.

Discussion:
66 comments Page 5 of 7.

Vinay said:   10 years ago
Please tell me how to find L.C.M in quick time for far numbers?

Teja said:   10 years ago
After seeing this question I first thought, this question might be from TRAIN AND DISTANCE.

How can one know that we have to LCM for such kind of questions?

Mahendra said:   10 years ago
How did you know that is to take LCM or HCF such types of questions?

Renuka said:   10 years ago
L.C.M means just remember that the highest number should be taken and common factor for the all given numbers. I hope yow will understand.

Madhavi said:   1 decade ago
Actually my problem is- taking out LCM will give when they'll meet i.e. it'll give the time at which they'll meet again but it's not necessary that they meet at the starting point? I guess dean's logic is correct.

Dean said:   1 decade ago
It can't be determined unless the whole length of the track is given. Anyway, they will meet on the track again after 46 m 12 s but not necessarily at the starting point.

Akshay said:   1 decade ago
Here every one should be at the same time according to question.

But after completion of 1 round not before it.

So each individual have to complete the round. That's why we have to consider their full time that's the reason to take LCM.

Senthil said:   1 decade ago
What is the need to take L.C.M in this question?

Ghanshyam said:   1 decade ago
And how to calculate HCF? Please tell me this answer also.

NaveenKK said:   1 decade ago
How we can get quick idea LCM as answer at exam time?


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