Fundamental Theorem Of Arithmetic

Fundamental Theorem of Arithmetic is where every composite number can be expressed in the form of primes.All the natural numbers can be expressed in the form of the product of its prime factors. Prime factors are the numbers which are divisible by 1 and itself only. For example the number 35 can be written in form of its prime factors as:

Fundamental Theorem of Arithmetic

All the natural numbers can be expressed in the form of the product of its prime factors. Prime factors are the numbers which are divisible by 1 and itself only. For example the number 35 can be written in form of its prime factors as:

35 = 7 × 5

Here, 7 and 5 are the prime factors of 35

The number 114560 can be represented as the the product of its prime factors by using prime factorization method,

114560 = \(2^7 ~×~5 ~×~ 179\)

So, we have factorized 114560 as product of the power of its primes. Therefore, we can say that every natural number can be expressed in the form of product of the power of its primes. This statement is known as the Fundamental Theorem of Arithmetic. This can be stated as follows:

Fundamental Theorem of Arithmetic Proof

A composite number is expressed in form of the product of primes and this factorization is unique apart from the order in which the prime factor occurs.

From this theorem we can also see that not only a composite number can be factorized as the product of their primes but also for each composite number the factorization is unique, not taking into consideration order of occurrence of the prime factors.

In simple words there exists only a single way to represent a natural number by the product of prime factors. This fact can also be stated as:

The prime factorization of any natural number is said to be unique for except the order of their factors.

In general, a composite number a can be expressed as,

a = \( p_1~ p_2~ p_3…………p_n, ~where~ p_1,p_2,p_3…………p_n\) are the prime factors of a written in ascending order i.e.\(p_1~≤~p_2~≤~p_3…………≤~p_n\)..

Writing the primes in ascending order makes the factorization unique in nature.

Let us now dig deeper and look into some fundamental theorem of arithmetic examples.

Example 1 : In a formula racing competition the time taken by two racing cars A and B to complete 1 round of the track is 30 minutes and 45 minutes respectively. After how much time will the cars meet again at the starting point?

Solution: As the time taken by car B is more compared to that of A to complete one round therefore it can be assumed that A will reach early and both the cars will meet again when A has already reached at the starting point. This time can be calculated by finding the L.C.M of the time taken by each.

30 = 2 × 3 × 5

45 = 3 × 3 × 9

The L.C.M is 90. Thus both the cars will meet at the starting point after 90 minutes.


Practise This Question

Equal chords subtend equal angles at the centre.