Sign Up For Free

**Join for FREE**,
and start talking with other members, weighing in on community polls,
and more.

Also, by registering and logging in you'll see fewer ads and pesky welcome messages (like this one!)

- Reply to threads, and start your own
- Create reports of your
**campus visits** - Share college
**photos**and**videos** **Find your dream college**, save your search and share with friends- Receive our
**monthly newsletter**

Home
/
College Discussion / College Admissions and Search / SAT and ACT Tests & Test Preparation / SAT Preparation

College Confidential’s “Dean,” Sally Rubenstone, put together 25 of her best tips. So far, the "25 Tips from the Dean" eBook has helped more than 10K students choose a college, get in, and pay for it. Get your free copy: http://goo.gl/9zDJTM

Archite
Posts: **118**Registered User Junior Member

Here is a picture of a math problem from a practice test I just took: [url]http://s1244.****/albums/gg580/agbond2013/?action=view¤t=fbae955f.jpg&evt=user_media_share[/url]

I've never seen the arch symbol before... What does it mean? The book explains the answer, but the answer is no help when I don't understand the context of the problem.

I've never seen the arch symbol before... What does it mean? The book explains the answer, but the answer is no help when I don't understand the context of the problem.

Post edited by Archite on

## Replies to: Math Q

369Registered User MemberA ∪ B means the set of those elements which are either in A, or in B, or in both

A ∩ B means the set that contains all those elements that A and B have in common

List of mathematical symbols - Wikipedia, the free encyclopedia

932Registered User MemberI think you should have learned some basics in middle school.

2,471Super Moderator Senior Member@Archite -

You'll never see these symbols on the SAT.

So the question is - as reiterated on CC gazillion times - why bother with the non-CB questions?

932Registered User Member2,471Super Moderator Senior MemberIt has been pointed out so many times on the CC that in your SAT practice you should stick with the CB authentic resources (there are plenty of them for the SAT I; SAT Subject tests is a different matter).

SAT questions from other than the CB sources are often ambiguous, outside of the SAT scope, overly difficult, and so on - which means, among other things, that creators of those questions are either not aware of exactly what is covered and what is not on the SAT or don't give a hoot about it.

991Registered User Member261Registered User Junior Member109Registered User Junior MemberNo. E (3/14)

Method 1 (works if you don't know that much about probability)

A = {1, 2, 4, 8}

B = {1, 3, 6, 8, 9}

C = A U B = {1, 2, 3, 4, 6, 8, 9}

D = A intersection B = {1, 8}

So here are the possible combinations, where the first number c is from C and the second number d is from D

1&1, 1&8, 2&1, 2&8, 3&1, 3&8, 4&1, 4&8, 6&1, 6&8, 8&1, 8&8, 9&1, 9&8 (14 combinations)

Of the above combinations, only 1&1, 3&1, and 9&1 yield an odd product. (3 combinations)

So the probability of choosing c and d so that cd is odd is 3/14.

Method 2 (how I prefer to solve the problem)

For the product of two integers to be odd, both numbers must be odd.

The probability of picking an odd number for C is 3/7

The probability of picking an odd number for D is 1/2

The probability of picking an odd number for C as well as for D is 3/7 * 1/2 = 3/14