Prime Factor Method for L.C.M

Q.

Find the prime factors of 136

Q. Four bells commence tolling together and then toll at intervals of 6, 7, 8 and 9 seconds respectively. After how many seconds do all the bells ring together?

1. 516
2. 504
3. 508
4. 512

Q. Determine the least number which when divided by 3, 4 and 5 leaves a remainder of 2 in each case. [3 MARKS]

Q.

Question 189

Determine the least number which when divided by 3, 4 and 5, leaves remainder 2 in each case.

Q. Write the largest 4-digit number and give its prime factorization.

Q.

What is the prime factorization of 36?

1. 
2. 
3. 
4. 

Q.

What is the smallest number which when divided by $15,20,36$ and $48$ gives the remainder $5$ in each case ?

Q.

Good afternoon mam/sir

I am Harshita and my query is:

Aarushi is helping her father plant trees to create a border around the backyard. Aarushi plants a tree every 25minutes and her father plants a tree every 15minutes. If they started together, how long will it be before they would finish planting a tree at the same time.

Thank you

Q.

Express the given number $1,500$ in terms of prime factorization.

Q.

Question 8

Find the least number which when divided by 6, 15 and 18 leave remainder 5 in each case.

Q. Determine the smallest 3-digit number which is exactly divisible by 6, 8 and 12.

Q.

Express the given number $2,904$ in terms of prime factorization.

Q. Find the LCM of 32, 64 & 128 by common division method.

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 prime factors of 64.

Q. Four bells commence tolling together at 1: 00 pm and toll at intervals of 2, 4, 6 and 8 minutes respectively. At what time will the bells toll together again?

1. 1 : 20 pm
2. 1 : 16 pm
3. 1 : 24 pm
4. 1 : 28 pm

Q. Six bells start tolling together and they toll at intervals of 2, 4, 6, 8, 10, 12 sec respectively, find
(i) after how much time will all six of them toll together?
(ii) how many times will they toll together in 30 min?

Q.

36 has only two factors that are prime numbers.

1. 1

2. 2

Q.

Select the option that correctly displays the prime factors of 36.

1. 
2. 
3. 
4. 

Q. Determine the smallest 3-digit number which is exactly divisible by 6, 8 and 12.

Q.

There are 3 taps. Water starts to drip from the three taps. A drop of water comes out of first, second and third tap every 2 seconds, 4 seconds and 7 seconds respectively. After how many seconds will the drops of water from all the three taps fall together?

1. 28 seconds

2. 14 seconds

3. 42 seconds

4. 56 seconds

Q.

Find the LCM of $80,96,125,160$

Q.

What is the prime factorization of 7?

1. 7

2. 14

3. $1\times 7$

4. $7\times 1$

Q.

Question 6

The traffic lights at three different road crossings change after every $48$ seconds, $72$ seconds and $108$ seconds respectively. If they change simultaneously at $7$ a.m., at what time will they change simultaneously again?

Q.

If $x$ is the LCM of a and b, a divides $x$ leaving zero remainder and integer quotient.

1. True

2. False

Q.

Select the option that correctly displays the prime factors of 36.

1. $2\times 2\times 3\times 3$

2. $4\times 3\times 3$

3. $6\times 6$

4. $2\times 3\times 6$

Q.

1. Find the H.C.F. of the following numbers using prime factorization method:

(viii) $66,102,138$

Q. Write the largest 4-digit number and give its prime factorization.

Q. Which is the least number which when divided by 6, 15 and 18 leave remainder 5 in each case?

1. 95
2. 185
3. 65
4. 100

Q.

Is $37$ a prime number? True/False.

1. True
2. False