Page 91 - ICSE Math 4

Step 4: Repeat the method ll all the numbers are reduced 2 11, 16
to 1 in the last row. 2 11, 8
Step 5: Mul ply all the prime numbers that are on the le 2 11, 4

column to get the L.C.M. of 11 and 16. 2 11, 2
11 11, 1
So, the L.C.M. of 11 and 16 = 2 × 2 × 2 × 2 × 11 = 176.
1, 1

Exercise 7.5

1. Find the H.C.F. of the following numbers by lis ng method.

(a) 6 and 10 (b) 72 and 81 (c) 15 and 36

(d) 14 and 28 (e) 36 and 45 (f) 10 and 14

2. Find the H.C.F. of 24, 60 and 72 using common division method.

3. List the fi rst fi ve common mul ples of the given numbers and then fi nd their
L.C.M.

(a) 2 and 3 (b) 3 and 5 (c) 40 and 60

(d) 15 and 20 (e) 12 and 16 (f) 25 and 30

4. Find the L.C.M. of the given numbers by common division method.

(a) 3 and 9 (b) 8 and 48 (c) 6, 8 and 12

(d) 2, 5 and 10 (e) 2, 4 and 6 (f) 15, 12 and 18

Review Exercise

1. Fill in the blanks.

(a) The mul ple of an ___________ number is always even.

(b) The smallest factor of any number is ___________.

(c) The greatest prime number less than 50 is ___________.
(d) ___________ is the smallest prime number.

(e) The ___________ mul ple of every number is the number itself.

(f) The fi rst three mul ples of 5 are ___________.

(g) The numbers having more than two factors are called ___________ numbers.

81