Advanced Math/SAT math

Advertisement

Expert: Robi Bhattacharjee - 9/25/2008


Question
Hello! The expert can't answer your question.

Your Question was:

Hey Robi
I need your help again!
Page 521
A list of numbers consists of p positive and n negative numbers. If a number is picked at random from this list, the probability that the number is  positive is (3/5). What is the value of (n/p)?

a) 3/8
b) 5/8
c) 2/3
d) 3/2
e) 8/3

Thanks in advance

Because Hello Emily,

Sorry about the late reply. This looks a bit too much like a homework question for me to help. I'm not supposed to help people on homework, sorry.

Hey Robi, I would like to clarify that this question is NOT a homework question. It's from the SAT review book OG (The Official SAT study guide) 2005 edition and beyond. It's on page 521 #12. I came across this question while reviewing for my SAT. :]


Answer
Hi Emily,

Sorry about the confusion,

Since there are p positive and n negative, the probability of a positive is p/(p +n) = 3/5 from given.


So 5p = 3p + 3n

2p = 3n

p = 3n/2.


so 2p = 3n so n/p = 2/3.

So the answer is (c) 2/3.


Feel free to ask,


Robi

Advanced Math

All Answers

Answers by Expert:

Ask Experts

Volunteer

Robi Bhattacharjee

Expertise

I can answer a variety of questions on mathematics. Questions on trigonometry, calculus(preferably single variable), algebra, geometry, and number theory will be answered. I cannot answer questions on abstract branches of mathematics such as group theory. I also cannot answer questions on statistics. In number theory, I can answer questions on congruences, prime numbers, units, functions, and the riemann-zeta function.

Experience

I have studied advanced math my entire life. I started calculus in sixth grade. I have attended numerous math competitions and I am attending math organizations such as the San-Diego math circle. Also, this year I have been invited to the USAMO which is a prestigious math competition (Every year the USAMO invites 500 students from across the USA to participate in this competition. The top 6 go to represent the USA in the International Math Olympiad).

Organizations
I am in the San Diego Math Circle

Education/Credentials
I am entering high school and have received a perfect score and the STAR test 5 times in a row. I also have gotten recognitions in the AMC 10, AIME, Math Counts, and ARML. Additionally, I have won the San Diego Math Olimpiad twice in a row.

©2012 About.com, a part of The New York Times Company. All rights reserved.