Question

50 bells $B_1,B_2,B_3,.......B_{50}$ start ringing together. The bells ring after every 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.....50 sec respectively.
In a span of 1 day , how many times do bells $B_{10},B_{20},....B_{50}$ ring together?

• A. 142
• B. 143
• C. 144
• D. 145

Answer 1

The correct option is C

144

$B_{10},B_{20},....B_{50}$ ring at the interval of 10,20,30,40,50 seconds respectively

So, LCM Of 10,20,30,40,50 is 600

So the bells will ring together every 600 seconds.

600 seconds = 10 minutes

There are 1440 minutes in a day. So the bells will ring together for $\frac{1440}{10}$ that is 144 times.