GRADE 6 math question?!?!

List all the factors of each number. How do you know you have found all the factors? Sort the factors into prime numbers and composite numbers. What do you notice? a) 34 b) 40 c) 72 d) 94

a) start with 1 and 34 and work inwards
write 1, 34 (leaving space for numbers in between)
then since 2 is a factor (i.e 34/2 is a whole number) you can write 1, 2, 17, 34 (leaving space for extra possible numbers however there are no more factors. so this is a composite number.
b) 1, 40
1, 2, 20, 40
1, 2, 4, 10, 20, 40
1, 2, 4, 5, 8, 10, 20, 40 (done this as well is a composite number)
c) 1, 72
1, 2, 36, 72
1, 2, 3, 24, 36, 72
1, 2, 3, 4, 18,24,36,72
1, ,2 ,3 ,4, 6, 12, 18, 24, 36, 72
1, ,2, 3, 4, 6, 8, 9, 12, 18, 24, 36, 72 (composite because it also has factors other than 1 and itself.)
d) 1, 94
1, 2, 47, 94

the only way i know to make sure their are no more factors is to keep trying to divide until you get a number you already tried.
for ex. in d) 94 you try dividing from 1-10 when you divide 94/10 you get 9.4 however you've already tried the number above and below 9.4 (9 and 10) therefore there are no more factors.

Good point... I'm not sure actually. I don't think there's a way to find out if you have all of them.