Here is a factor tree of 39: 39 3 x 13 Since these are prime numbers, the factor tree is finished. The prime factors of 39 are 3 and 13.
39 3,13
39 3,13
39 3,13
39 3,13
39 3,13
39 13,3 3 x 13 = 39
Factor tree: ............78 .........../..\ ..........2..39 ............../..\ ............3...13 78 = 2 x 3 x 13
195 5, 39 5, 3, 13
351 / \ 39 9 / \ / \ 13 3 3 3
The greatest factor is 39.
where is .39 on a ruler