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Step 4: Divide 10 by the smallest prime number, that is 2 and write the quotient 5 below
10.

Step 5: Divide 5 by the smallest prime number , that is 5 itself and write the quotient 1
below 5.

Step 6: Now write all the prime factorization of 80.

Step 7: 2x2x2x2x5.

Example2: Find the prime factorization of 91

Step1: 2 is the smallest prime number. But it cannot divide 91 exactly. So, consider 3., it
cannot divide by 3 and next 5 . Now consider 7.

Step2: Now, 7 cannot be divide by 13. Consider the next smallest prime number 5, it
cannot divide by 5, 7, & 11. So we consider 13.

The prime factors of 91 are 7 × 13.

 Write the primefactorisation using factor tree method

The first step in making a factor tree is to find a pair of factors whose product is
the number that we are factoring. These two factors are the first branching in
the factor tree. There are often several different pairs of factors that we could
choose to begin the process. The choice does not matter; we may begin with
any two factors. We repeat the process with each factor until each branch of
the tree ends in a prime. Then the prime factorization is complete.

Example 1 : Write the prime factorization of 36 by factor tree method.