Question

electronic device make a beep after every 45 minutes 1 hour 1 hour 15 minutes and 1 hour 30 minutes respectively all the device be put together at 12 noon at what time will the will they be put together again a) 3 a.m b) 4 a.m c) 5 a.m d) 12 mid night​

Answer 1

Answer:

a=3am

Step-by-step explanation:

Answer 2

Answer:

9 a.m

Step-by-step explanation:

First device beeps in every 30min

Second device beeps in every 60min

Third device beeps in every 90min

Fourth device beeps in every 105min

That means together they beep after how many minutes

We calculate LCM(30,60,90,105)

30=2×3×5

60=2×2×3×5

90=2×3×3×5

105=3×5×7

So, LCM=2

2

×3

2

×5×7=1260

⇒ ie, in

60

1260

=21hrs they beep together.

⇒ All beeped together after 12 noon at 21 hrs later. i.e, (12+21)hrs=9a.m.

∴ Next they will beeped together at 9a.m.