3x7=21 3 and 7 are prime numbers, so 3x7 is the factor tree of the number 21.
First, find two numbers that when multiplied together equal 189. I can tell by looking at the number that it is divisible by 9. Any number whose digits add up to a number divisible by 9 is also divisible by 9. 1 + 8 + 9 = 18, which is divisible by 9. 189 ÷ 9 is 21. So, the top of our factor tree is: 189 9 x 21 Now, determine two pairs of numbers that when multiplied together, one pair will equal 9 and the other pair will equal 21. 9 = 3 x 3 and 21 = 7 x 3. So, now our factor tree is: 189 9 x 21 (3x3) x (7x3) You would continue doing this until you no more numbers can be factored. Since 3 and 7 are prime numbers, the factor tree is finished. The factor tree shows that the prime factorization of 189 is 3 x 3 x 3 x 7 or 33 x 7.
Factor tree of 40: 40 20,2 10,2,2 5,2,2,2
Since 21 is a factor of 105, it is automatically the GCF.
Here is a factor tree of eight: 8 / \ 4 2 / \ 2 2
21
3x7=21 3 and 7 are prime numbers, so 3x7 is the factor tree of the number 21.
21 3,7
21/ \7 3
21 3,7
21 is equal to 3 times 7.
21 3,7
it is ^ ^ 21 5 ^ 7 3
84 42 2 21 2 2 square root of 21 84 2 42 factor tree 6 7 2 3
21 3,7 3 x 7 = 21
1
3 and 7