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 ?
A. 4
B. 10
C. 15
D. 16
Answer: Option D
Solution(By Examveda Team)
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
$$\frac{{30}}{2}$$ + 1 = 16 times
Join The Discussion
Comments ( 8 )
Related Questions on Problems on H.C.F and L.C.M
why did we add 1
why adding plus 1
in six bell=2,4,6,8,10,12.,if we count the digit of all given no.=6,
so answer should be the vice versa of question ,means
so in 30 min tolling of bell like,0,2,4,6,8,10,12,14,16,18,20,22,24,26,28,30.
total no of digit =16,
so ans =16.
note=counting should be starting from the 0.
But,if it start at 1 i.e last time they toll together at 11,then it should be 1,3,5,7,9,11,13,15,17,19,21,23,25,27 and 30
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
They all missed their 24
2,4,6,8,10,12 lcm is 120
1min=60 sec
120 sec= 2 min
.: ever 2 mins one bell
30 mins
0,2,4,6,8,10,12,14,16,18,20,22,26,28,30
Count all series =16 time
Ans-C
I don't understand how 16 times they will toll together. According to me the answer should be 15 times.