## darkbbn 3 years ago If C = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10} and D = {numbers divisible by 3 from 1 to 21}, what is C ∩ D? {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 18, 21} {3, 6, 9, 12, 15, 18, 21} {3, 6, 9} { }

1. Grazes

I think it would help if you listed the numbers in set D

2. Grazes

Basically, D={3,6,9,12,15,18,21} You need to find numbers that are in set A AND set D to get C ∩ D

3. darkbbn

Uhh...?

4. Grazes

Do you understand the part about getting the numbers in set D?

5. darkbbn

No

6. Grazes

btw, I meant sets C and D.

7. Grazes

Numbers divisible by 3 from 1-21? 3 is divisible by 3 because it equals a whole number(1). 6/3=2 (Also a whole number). 9/3=3... etc. Better?

8. darkbbn

Yah i understand how to do that but i dont understand how to get the answer :/ Could u walk me throug it

9. Grazes

Sure. Do we agree that D={3,6,9,12,15,18,21}?

10. darkbbn

Yes

11. Grazes

∩ means intersection which also means that the numbers in that set MUST be in the 2 sets surrounding it.

12. Grazes

It basically means that the numbers in the intersection of the sets must be in BOTH sets.

13. Grazes

So if A={2,4,6,7} and B={3,4,5,6}, A∩B would be {4,6} because 4 and 6 are in both sets A and B

14. darkbbn

Oh ok

15. Grazes

Now that you have both sets, match 'em up and see which numbers are in both. C = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10} D={3,6,9,12,15,18,21}

16. darkbbn

3,6,9

17. darkbbn

Ohh Ty ^^ Can u help me with another on? please?

18. Grazes

19. Grazes

Sure.

20. darkbbn

If A = {vowels in the English alphabet} and B = {consonants in the English alphabet}, what is A B? {all letters in the English alphabet} {a, e, i, o, u} {b, c, d, f, g, h, j, k, l, m, n, p, q, r, s, t, v, w, x, y, z} { }

21. Grazes

List both sets A and B, please. Also, I don't know what the relation between A and B is because you don't have anything in between A and B

22. darkbbn

there is supossed to be a " U" smble between the A and b on the last sentence and it stated A and B

23. Grazes

That's easy, then.The answer is just all the letters of the alphabet. Consonants+vowels=letters of the alphabet.

24. darkbbn

O.o wow didnet think about that lol Thanks

25. darkbbn

Ill be posting a few more u acn help if u want

26. Grazes

This would be a lot easier if OpenStudy made a Apple Application so I could write everything out...

27. darkbbn

They have a draw thingy

28. Grazes

doesn't help. Have you tried it? My drawings always look atrocious.

29. darkbbn

lol ssame do u kno how to to dthis? If A = {0, 1, 2, 3} and B = {…−3, −2, −1}, what is A ∩ B? {…−3, −2, −1, 0, 1, 2, 3, …} {…−3, −2, −1} {0, 1, 2, 3} { }

30. Grazes

{}. Empty set.

31. Grazes

It can also be |dw:1347317896078:dw| Not a circle, btw

32. darkbbn

Ok ty and haha kinda looks like one ;)