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. 3)
3.
Six bells commence tolling together and toll at intervals of 2, 4, 6, 8 10 and 12 seconds respectively. In 30 minutes, how many times do they toll together ?
Answer: Option
Explanation:
L.C.M. of 2, 4, 6, 8, 10, 12 is 120.
So, the bells will toll together after every 120 seconds(2 minutes).
| In 30 minutes, they will toll together | 30 | + 1 = 16 times. |
| 2 |
Discussion:
170 comments Page 3 of 17.
Sagar said:
7 years ago
As it is clear from the question and the answer provided that the bells Are going to toll together after every 2 min.
So, in the given interval of 30 min.
They will be going to toll 30/2 that is 15 times and early in the question they have mentioned that the bells are already toll together at once.
So, the answer is 30/2 + 1= 16 times.
So, in the given interval of 30 min.
They will be going to toll 30/2 that is 15 times and early in the question they have mentioned that the bells are already toll together at once.
So, the answer is 30/2 + 1= 16 times.
(2)
Chojoy said:
6 years ago
You can also use AP(Arithmetic Progression) method to solve this problem.
Since the given tolling interval are in AP,ie 2 4 6 8 10 12........ , and nth time is 30min.
HENCE, using AP formula, we have;
T(N)=a+(n-1)d
a=2, d=4-2 ie d=2, n=?
30=2+(n-1)2
30=2+2n-2
ie, 30=2n
therefore, n=15.
Since we have to consider first toll, add+1 to n.
Therefore, the answer is 15+1=16.
Since the given tolling interval are in AP,ie 2 4 6 8 10 12........ , and nth time is 30min.
HENCE, using AP formula, we have;
T(N)=a+(n-1)d
a=2, d=4-2 ie d=2, n=?
30=2+(n-1)2
30=2+2n-2
ie, 30=2n
therefore, n=15.
Since we have to consider first toll, add+1 to n.
Therefore, the answer is 15+1=16.
(2)
Revathy said:
1 decade ago
Why do you divide 30 by 2?
(1)
Nakum Paras said:
1 decade ago
Actually got solution.
All bells starting from 1 second at a time 1 time bells tolling at a time.
1st bell tolling every 2 sec means 2, 4, 6, 8,...120...240... 360....480
2nd bell tolling every 4 sec means 4, 8, 12, 16...120...240...360...480
3rd bell tolling every 6 sec means 6, 12, 18, 24...120...240...360...480
4th bell tolling every 8 sec means 8, 16, 24...120...240...360...480
5th bell tolling every 10 sec means 10, 20, 30...120...240...360...480
6th bell tolling every 6 sec means 12, 24, 36...120...240...360...480
So 1 sec =1 time tolling at a time.
120 sec = 2 time tolling at a time.
240 sec = 3 time tolling at a time.
360 sec = 4 time tolling at a time.
4800 sec = 5 time tolling.
600 sec = 6 time tolling at a time.
.
.
Last 1800 sec = 16 time tolling at a time.
Total time bells tolling at a time =16 times.
All bells starting from 1 second at a time 1 time bells tolling at a time.
1st bell tolling every 2 sec means 2, 4, 6, 8,...120...240... 360....480
2nd bell tolling every 4 sec means 4, 8, 12, 16...120...240...360...480
3rd bell tolling every 6 sec means 6, 12, 18, 24...120...240...360...480
4th bell tolling every 8 sec means 8, 16, 24...120...240...360...480
5th bell tolling every 10 sec means 10, 20, 30...120...240...360...480
6th bell tolling every 6 sec means 12, 24, 36...120...240...360...480
So 1 sec =1 time tolling at a time.
120 sec = 2 time tolling at a time.
240 sec = 3 time tolling at a time.
360 sec = 4 time tolling at a time.
4800 sec = 5 time tolling.
600 sec = 6 time tolling at a time.
.
.
Last 1800 sec = 16 time tolling at a time.
Total time bells tolling at a time =16 times.
(1)
Surajbhan singh said:
6 years ago
Why 1 is added your answer in the question. Read it once again carefully.
(1)
Punk said:
2 decades ago
Why 1 is added? please explain.
KUSHAL said:
1 decade ago
Super explanation sundar.
Vishnu said:
1 decade ago
So We need to count that first commence according to your answer.
But according to the question we need to find the time after first tolling together na ?
But according to the question we need to find the time after first tolling together na ?
Mehar said:
1 decade ago
WoW...super explanation .thank you:)
Sathya said:
1 decade ago
Excellent sravan now I understand everything in the question n wt you said. Its really very helpful to me. , AND YOUR EXPLANATION IS VERY VERY CLEAR.
THAN YOU VERY MUCH sravan!
THAN YOU VERY MUCH sravan!
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