Three bells are ringing continuously at intervals of $30\min ,36\min ,45\min$  respectively. At what time will they ring again together, if they ring simultaneously at $8a.m$  is

To find the time when they ring again together, we have to find $L.C.M$  of $30,36,45$ .

$L.C.M=5\times 3\times 2\times 3\times 2$

$=180$

The bells will ring together again

After $180$  minutes. The time $180$  minutes $\left(3hrs\right)$  after $8a.m$ .

So bells will ring together again at $11a.m$ .