Use Prime Factorisation to Find LCM

Q.

If the two numbers are $35$ and $49$, find a third number such that the$\mathrm{LCM}$ of the three numbers is $1225$.

Q.

Find the smallest number which when increased by $17$ is exactly divisible by $520$ and $468$.

Q.

Find out the LCM of $6$ and $9$

Q.

Three boys A, B and C a]can go round a circular pathway in $3min20sec,3min40secand4min$ respectively. If they start simultaneously from the same place and at the same time, when will they all meet next?

Q.

Three athletes A, B, C are participating in a racing event. They start running together. A takes 30 seconds to complete one round on the track, B takes 40 seconds and C takes 45 seconds. What is the minimum number of seconds after which will they all be at the same place again?

1. 180 seconds

2. 240 seconds

3. 360 seconds

4. 720 seconds

Q. Find the LCM of 5, 8, 10.

1. 40

Q. The LCM of 36 and 45 is ___.

1. 220
2. 105
3. 180
4. 108

Q.

Three cannons fire shots at intervals of 12 seconds, 18 seconds and 60 seconds respectively. If they start firing at the same time, then after how many seconds will they fire together again?

1. 3 minutes

2. 4 minutes

3. 5 minutes

4. 6 minutes

Q. The least number which is exactly divisible by 20, 30 and 40 is ____.

1. 120
2. 100
3. 180
4. 150

Q. Three bells start chiming at the same time and they chime at the interval of 56 seconds, 72 seconds and 120 seconds respectively. After how many seconds will they chime again together?

1. 1200 seconds
2. 1120 seconds
3. 2520 seconds
4. 4320 seconds

Q. Find the LCM of 5, 8, 10.

1. 40

Q. Three bells toll together at intervals of 9, 12 and 15 minutes. If they start tolling together now, after how much time will they toll together next?

1. 1 hour
2. 2 hours
3. 3 hours
4. 4 hours

Q.

Find the smallest number which is completely divisible by 28 and 42.

1. 48

2. 28

3. 84

4. 14