Question

Find the HCF of 25 and 30.
A. 25
B. 6
C. 1
D. 5

Answer 1

Hint: Recall the definition of HCF that is ‘Highest factor of all the common factor in the given number’
So we can factorise given numbers and then we can find the highest common factor by writing prime factors of those numbers.
Complete step-by-step answer:
Given numbers are $$25,30$$
In order to find the Highest common factor. First we will find the factor of all the given numbers.
Factor of 25 is

Hence we can write 25 as
$\Rightarrow 25=5\times 5\times 1$
Factor of 30 is

Hence we can write 30 as
$\Rightarrow 30=2\times 3\times 5\times 1$
Highest common factor = 5
HCF = 5
Hence option D is correct.
Note: Another direct method for this problem is as follows. We know that factor of 1 is only $${}^{\prime }{1}^{\prime }$$. so, if any problem has a group of numbers containing $${}^{\prime }{1}^{\prime }$$ to find HCF. The common factor is also will be only $${}^{\prime }{1}^{\prime }$$.
Hence the highest common factor is also$${}^{\prime }{1}^{\prime }$$.
So, we can conclude that HCF of a group of numbers containing $${}^{\prime }{1}^{\prime }$$ is also $${}^{\prime }{1}^{\prime }$$.