4 bells first begin to toll together with an intervals of 5, 10, 15 & 20 sec. How many times does they toll together in an hr? Choose the correct choice from the following options.
A) 50 B) 60 C) 70 D) 80 E) 90
5|5, 10, 15, 20   2|1, 2, 3, 4   |1, 1, 3, 2   L.C.M of 5, 10, 15, 20 is 60   60 times   60
<result>B</result>
4 bells first begin to toll together with an intervals of 5, 10, 15 & 20 sec. How many times does they toll together in an hr?