Question

Que. 3. Four runners started running simultaneously from a point on a circular track. They took 200 s, 300 s, 360 s and 450 s to complete one round. After how much time do they meet at the starting point for the first time?

Que 4. The traffic lights at three different road crossings change after 24 s, 36 s and 54 s respectively. If they all change simultaneously at 10:15:00 a.m., then at what time will they again change simultaneously?​

Answer 1

Answer:

3 ) Required time = LCM of 200, 300, 360 and 450 seconds

We find , LCM of 200, 300, 360 and 450 seconds = 1800 seconds

∴ Required time = 1800 seconds

Step-by-step explanation:

4 ) LCM of left(24, 36, 54)

⇒ 12 × 2 × 3 × 3 = 216 sec

⇒ They will change simultaneously after every 216 seconds

$\frac{216}{60} \: \: \: \: = \: 3 \: \frac{36}{60}$

⇒ They change 1st at 10:15:00 AM

So, again they change at = 10:18:36 AM