EXERCISE 3.1

1). Write all the factors of the following numbers.
a) 24
Ans.    
1 x 24 =24                  
2 x 12 = 24
3 x 8 =24
4 x 6 = 24
Therefore, the factors of 24 are 1 , 2 , 3 , 4 , 6 , 8 , 12 , 24.

b) 15
Ans.    
1 x 15 = 15                 
3 x 5 = 15
Therefore, the factors of  15  are 1 , 3 , 5 and 15.

c) 21
Ans.    
1 x 21 = 21
3 x 7 = 21                   
7 x 3 = 21
Therefore, the factors of 21 are 1, 3, 7 and 21.

d) 27
Ans.    
1 x 27 = 27
3 x 9 = 27
Therefore, the factors of  27  are 1 , 3 , 9 and 27.

e) 12
Ans.  
1 x 12 = 12
2 x 6 = 12
3 x 4 = 12
4 x 3 = 12
Therefore, the factors of 27 are 1 , 3 , 9 and 27.

f) 20
Ans.    
1 x 20 = 20
2 x 10 = 20
4 x 5 = 20
Therefore, the factors of 20 are 1 , 2 , 4 , 5 , 10 and 20.

g) 18
Ans.    
1 x 18 = 18
2 x 9 = 18
3 x 6 = 18
6 x 3 = 18
Therefore, the factors of 18 are 1 , 2 , 3 , 6 , 9 and 18.

h) 23
Ans.    
1 x 23 = 23
23 x 1 = 23
Therefore, the factors of 23 are 1 and 23.

i) 36
Ans.    
1 x 36 = 36
2 x 18 = 36
3 x 12 = 36
4 x 9 = 36
6 x 6 = 36
Therefore, the factors of 36 are 1 , 2 , 3 , 4 , 6 , 9 , 12 , 18 and 36.

2). Write first five multiples of:
a) 5
Ans.    
The required multiples are
5 x 1 = 5
5 x 2 = 10
5 x 3 = 15
5 x 4 = 20
5 x 5 = 25
Hence, the first five multiples are 5 , 10 , 15 , 20 and 25.

b) 8
Ans.    
8 x 1 = 8
8 x 2 = 16
8 x 3 = 24
8 x 4 = 32
8 x 5 = 40
Hence, the first five multiple of 8 are 8 , 16 , 24 , 32 and 40.

c) 9
Ans.    
9 x 1 = 9
9 x 2 = 18
9 x 3 = 27
9 x 4 = 36
9 x 5 = 45
Hence, the first five multiple of 9 are 9 , 18 , 27 , 36 and 45

 

3). Match the items in column 1 with the items in column 2.
       Column 1                                                        Column 2

  1. 35                                                                      a) Multiple of 8
  2. 15                                                                      b) Multiple of 7
  3. 16                                                                      c) Multiple of 70
  4. 20                                                                     d) Factor of 30
  5. 25                                                                     e) Factor of 50
                                                                              f)Factor of 20

Ans.     i) b       ii) d      iii) a      iv) f       v) e

4).Find all the multiples of 9 upto 100
Ans.    
9 x 1 = 9
9 x 2 = 18
9 x 3 = 27
9 x 4 = 36
9 x 5 = 45
9 x 6 = 54
9 x 7 = 63
9 x 8 = 72
9 x 9 = 81
9 x 10 = 90
9 x 11 = 99
Therefore, all the multiples of 9 upto 100 are 9 , 18 , 27 , 36 , 45 , 54 , 63 , 72 , 81 , 90 , 99.