Find the HCFof the following pairs of number by listing the factors

(a)  24,72    (b)  45,81    (c)  18,21    (d)  52 ,78    (e)  69,39   (f)   108,72    (g) 45,64   (h)  27,63

how to do this ?

Answer :

We find HCF by making factors , As  :

a ) HCF  ( 24 , 72 )

24  =  2 $\times$ 2 $\times$ 2 $\times$ 3
And
72  =  2 $\times$ 2 $\times$ 2 $\times$ 3 $\times$  3

So,

HCF (  24 , 72 ) =  2 $\times$ 2 $\times$ 2 $\times$ 3  =  24                                     ( Ans )

b  ) HCF  ( 45 , 81 )

45  =  3 $\times$ 3 $\times$ 5
And
81  =  3 $\times$ 3 $\times$ 3 $\times$ 3

So,

HCF (  45 , 81 ) =  3 $\times$ 3  =  9                                     ( Ans )

c  ) HCF  ( 18 , 21 )

18  =  2 $\times$ 3 $\times$ 3
And
21  =  3 $\times$  7

So,

HCF (  18 ,21 ) =  3                                    ( Ans )

Similarly , You can solve rest of HCF by your self and if you still have any doubts , Please get back to us ,So we can help you precisely  .