Three bells ring simultaneously at 11 am. They ring at regular intervals of 20 min, 30 min, 40 min, respectively. The time when all the three ring together next is [SSC (CGL) 2011] |
A) 2 pm
B) 1 pm
C) 1 : 15 pm
D) 1 : 30 pm
Correct Answer: B
Solution :
Required time = LCM of 20, 30 and 40 |
\[\text{LCM}=10\times 2\times 3\times 2=120\] |
Hence, the bells will simultaneously ring after 2 h, i.e. at 1 pm. |
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