Page 88 - ICSE Math 4

2. Which of the following numbers are divisible by 3?
(a) 83 (b) 126 (c) 219 (d) 317 (e) 543 (f) 906

3. Which of the following numbers are divisible by 4?

(a) 48 (b) 76 (c) 627 (d) 266 (e) 716 (f) 834

4. Which of the following numbers are divisible by 5?

(a) 160 (b) 295 (c) 384 (d) 432 (e) 730 (f) 810
5. Which of the following numbers are divisible by 9?

(a) 81 (b) 207 (c) 438 (d) 603 (e) 61 (f) 373

6. Which of the following numbers are divisible by 10?

(a) 80 (b) 100 (c) 209 (d) 708 (e) 560 (f) 75

Highest Common Factor (H.C.F.)

Highest Common Factor (H.C.F.) is the highest or the greatest factor that divides all the
given numbers without leaving any remainder. It is also called the Greatest Common
Factor (G.C.F.).

H.C.F. of two or more numbers can be obtained by two methods. These methods are the
lis ng method and the common division method. Let’s learn about them.

Listing Method

In this method, we list the factors of the given numbers. Then we fi nd the highest or the
greatest factor among the common factors of the given numbers.

Example 14: Find the H.C.F. of 12 and 18 by lis ng method.
Remember
Solu on: Step 1: List all the factors of 12 and 18.
• The numbers with
Factors of 12 = 1, 2, 3, 4, 6 and 12 H.C.F. as 1 are called
co-prime numbers.
Factors of 18 = 1, 2, 3, 6, 9, and 18
• The H.C.F. is always
Step 2: Compare and iden fy the common smaller than or equal
to the smaller number.
factors of 12 and 18 among the list
of factors.
Factors of 12 = 1 , 2 , 3 , 4, 6 and 12

Factors of 18 = 1 , 2 , 3 , 6 , 9 and 18

Step 3: Write the common factors of 12 and 18.

Common factors of 12 and 18 = 1, 2, 3 and 6

Step 4: Write the highest factor among the common factors as H.C.F. of 12
and 18. Here, 6 is the highest common factor.
So, the H.C.F. of 12 and 18 is 6.

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