Study Notes of HCF and LCM and Aptitude Quiz TIPS FOR SOLVING QUESTIONS RELATED TO HCF and LCM: Prime number : A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. For example, 2, 3, 5, 7, 11, 13, etc. are prime numbers. Co-Prime Number: Two numbers are said to be relatively prime, mutually prime, or co-prime to each other when they have no common factor or the only common positive factor of the two numbers is 1. In other words, two numbers are said to be co-primes if their H.C.F. is 1. Factors: The numbers are said to be factors of a given number when they exactly divide that number. Thus, factors of 18 are 1, 2, 3, 6, 9 and 18. Common Factors: A common factor of two or more numbers is a number which divides each of them exactly. Thus, each of the numbers – 2, 4 and 8 is a common factor of 8 and 24. Multiple: When a number is exactly divisible by another number,...