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## Selina Concise Mathematics Class 6 ICSE Solutions Chapter 8 HCF and LCM

**Selina Publishers Concise Mathematics Class 6 ICSE Solutions Chapter 8 HCF and LCM**

### HCF and LCM Exercise 8A – Selina Concise Mathematics Class 6 ICSE Solutions

Question 1.

Write all the factors of :

(i) 15

(ii) 55

(iii) 48

(iv) 36

(v) 84

Solution:

Question 2.

Write all prime numbers :

(i) less than 25

(ii) between 15 and 35

(iii) between 8 and 76

Solution:

Question 3.

Write the prime-numbers from :

(i) 5 to 45

(ii) 2 to 32

(iii) 8 to 48

(iv) 9 to 59

Solution:

Question 4.

Write the prime factors of:

(i) 16

(ii) 27

(iii) 35

(iv) 49

Solution:

Question 5.

If P_{n} means prime factors of n, find:

(i) p_{6}

(ii) P_{24}

(iii) p_{50}

(iv) P_{42}

Solution:

### HCF and LCM Exercise 8B – Selina Concise Mathematics Class 6 ICSE Solutions

Question 1.

Using the common factor method, find the H.C.F. of :

(i) 16 and 35

(ii) 25 and 20

(iii) 27 and 75

(iv) 8, 12 and 18

(v) 24, 36, 45 and 60

Solution:

Question 2.

Using the prime factor method, find the H.C.F. of:

(i) 5 and 8

(ii) 24 and 49

(iii) 40, 60 and 80

(iv) 48, 84 and 88

(v) 12, 16 and 28

Solution:

Question 3.

Using the division method, find the H.C.F. of the following :

(i) 16 and 24

(ii) 18 and 30

(iii) 7, 14 and 24

(iv) 70,80,120 and 150

(v) 32, 56 and 46

Solution:

Question 4.

Use a method of your own choice to find the H.C.F. of :

(i) 45, 75 and 135

(ii) 48, 36 and 96

(iii) 66, 33 and 132

(iv) 24, 36, 60 and 132

(v) 30, 60, 90 and 105

Solution:

Question 5.

Find the greatest number that divides each of 180, 225 and 315 completely.

Solution:

Question 6.

Show that 45 and 56 are co-prime numbers.

Solution:

Question 7.

Out of 15, 16, 21 and 28, find out all the pairs of co-prime numbers.

Solution:

Question 8.

Find the greatest no. that will divide 93, 111 and 129, leaving remainder 3 in each case.

Solution:

### HCF and LCM Exercise 8C – Selina Concise Mathematics Class 6 ICSE Solutions

Question 1.

Using the common multiple method, find the L.C.M. of the following :

(i) 8, 12 and 24

(ii) 10, 15 and 20

(iii) 3, 6, 9 and 12

Solution:

Question 2.

Find the L.C.M. of each the following groups of numbers, using

(i) the prime factor method and

(ii) the common division method :

(i) 18, 24 and 96

(ii) 100, 150 and 200

(iii) 14, 21 and 98

(iv) 22, 121 and 33

(v) 34, 85 and 51

Solution:

Question 3.

The H.C.F. and the L.C.M. of two numbers are 50 and 300 respectively. If one of the numbers is 150, find the other one.

Solution:

Question 4.

The product of two numbers is 432 and their L.C.M. is 72. Find their H.C.F.

Solution:

Question 5.

The product of two numbers is 19,200 and their H.C.F. is 40. Find their L.C.M.

Solution:

Question 6.

Find the smallest number which, when divided by 12, 15, 18, 24 and 36 leaves no remainder

Solution:

Question 7.

Find the smallest number which, when increased by one is exactly divisible by 12, 18, 24, 32 and 40

Solution:

Question 8.

Find the smallest number which, on being decreased by 3, is completely divisible by 18, 36, 32 and 27.

Solution:

### HCF and LCM Revision Exercise – Selina Concise Mathematics Class 6 ICSE Solutions

Question 1.

Find the H.C.F. of :

(i) 108, 288 and 420

(ii) 36, 54 and 138

Solution:

Question 2.

Find the L.C.M. of:

(i) 72, 80 and 252

(ii) 48, 66 and 120

Solution:

Question 3.

State true or false : Give an example.

(i) H.C.F. of two prime numbers is 1.

(ii) H.C.F. of two co-prime numbers is 1.

(iii) L.C.M. of two prime numbers is equal to their product.

(iv) L.C.M. of two co-prime numbers is equal to their product.

Solution:

Question 4.

The product of two numbers is 12096 and their H.C.F. is 36. Find their L.C.M.

Solution:

Question 5.

The product of the H.C.F. and the L.C.M. of two numbers is 1152. If one number is 48, find the other one.

Solution:

Question 6.

(i) Find the smallest number that is completely divisible by 28 and 42.

(ii) Find the largest number that can divide 28 and 42 completely.

Solution:

Question 7.

Find the L.C.M. of 140 and 168. Use the L.C.M. obtained to find the H.C.F. of the given numbers.

Solution:

Question 8.

Find the H.C.F. of 108 and 450 and use the H.C.F. obtained to find the L.C.M. of the given numbers.

Solution: