Question

What is the GCF of $ 15 $ and $ 60 $ ?

Answer 1

Hint: Here, first we will find prime factorization of the given numbers and then accordingly on the basis of the prime factors we will find the greatest common factor (GCF). GCF is the greatest or the largest common factor between two or more given numbers. It is also known as the Highest common factor.

Complete step-by-step answer:
First find the prime factors of the given numbers.
 Prime factorization is the process of finding which prime numbers can be multiplied together to make the original number, where prime numbers are the numbers greater than $ 1 $ and which are not the product of any two smaller natural numbers. For Example: $ 2,{\text{ 3, 5, 7,}}...... $ $ 2 $ is the prime number as it can have only $ 1 $ factor. Factors are the number $ 1 $ and the number itself.
 $
  15 = \underline {3 \times 5} \\
  60 = 2 \times 2 \times \underline {3 \times 5} \;
  $
The common factors in all the two given numbers are $ 3 $ and $ 5 $
Hence, the greatest common factor of $ 15 $ and $ 60 $ is $ = 3 \times 5 = 15 $
So, the correct answer is “15”.

Note: Prime factorisation can also be done by the factor tree method. It is the factor-tree which shows the prime factors of the composite number in the form tree. One can get different factor trees to find the same prime factorization of the same composite number. Be good in multiples and remember it at least twenty. HCF (Highest common factor is also known as the greatest common factor. LCM (Least common multiple) is also known as the least common divisor.