QUESTIONS FROM GRE EXAM ( I NEED HELP)

Subject: QUESTIONS FROM GRE EXAM ( I NEED HELP) Fri Nov 06, 2009 6:34 am

Dr. Colin, I took GRE exam last week, and it had a lot of problems from Statistics& Probability. I want you to solve these problems because I saw them in last GRE exam. I solved all of them and I have remembered the answer of each, but I am not sure if my solutions were correct or not:
1st question: My answer was 16
2nd question: My answers were
a-
1-0.2
2-0.10
b- 0.53
Please tell me if my solution was correct otherwise I appreciate you if you give me a correct answer.
Q1: The fourth grade school at School X is made up of 300 students who have a total weight of 21600 pounds. If the weight of these of fourth graders has a normal distribution and the standard deviation equals 12 pounds . Approximately what percentage of the fourth graders weighs more than 84 pounds?
Q2: Fifteen marbles are placed in a bowl; some are red, and all of the others are blue. If the number of red marble is one more than the number of the blue marbles, a- what is the probability that both of marbles taken from the bowl are blue for these situations?
1.Select two times without replacement?
2.Select three times with replacement?
B-Select two times W/O replacement, what is the probability that one of them is red or blue?

This question is not from GRE exam, but I want to know how I can solve it.
Q3: Dr.Colin is going ( I mean that you are planning to roll a dice before I talk to you?? “Grammar class”) to roll a pair of six-sided dice, one at a time. What is the probability that he rolls a 3 and then a 4 OR a 5 and the prime number? (Please give me answer with appropriate details)
(Hint: the prime number is a number that is divisible only by itself and 1. For example, 2,3,5,7,11,13,17,19,23,27,29……etc.)
Q3 I want you to give me a lecture about permutations and combinations and how I can use each of them when I want to order or slot something.

Best Regards,
Saeed J. Almalowi
Mechanical Engineer

Admin Posts : 38 Join date : 2009-10-23

My answer for question#1 was:
Average= the total weight / number of stendents = 21600/300=216/3=72
standard Deviation = 12
So, 72+12=84
percentage of the fourth graders weighs more than 84 pounds=100-84=16

Posts : 5 Join date : 2009-10-27

Admin wrote:: My answer for question#1 was:
Average= the total weight / number of stendents = 21600/300=216/3=72
standard Deviation = 12
So, 72+12=84
percentage of the fourth graders weighs more than 84 pounds=100-84=16

Q1: The fourth grade school at School X is made up of 300 students who have a total weight of 21600 pounds. If the weight of these of fourth graders has a normal distribution and the standard deviation equals 12 pounds . Approximately what percentage of the fourth graders weighs more than 84 pounds?

Average=72
S.D=12
84 between Average has 1 S.D gap
According to normal distribution, we should know
QUESTIONS FROM GRE EXAM ( I NEED HELP) File:Standard_deviation_diagram

QUESTIONS FROM GRE EXAM ( I NEED HELP) File:Standard_deviation_diagram

so from 0 to 1 S.D is 84%
1-0.84= 0.16 = 16%
And your answer is correct just lucky...............
if the question change number, you will be wrong!

Posts : 5 Join date : 2009-10-27

Q2: Fifteen marbles are placed in a bowl; some are red, and all of the others are blue. If the number of red marble is one more than the number of the blue marbles, a- what is the probability that both of marbles taken from the bowl are blue for these situations?
1.Select two times without replacement?
2.Select three times with replacement?
B-Select two times W/O replacement, what is the probability that one of them is red or blue?

1. 8 red and 7 blue

P(blue and blue)= 7/15* 6/14= 0.2

2
P(blue and blue and blue)= 7/15* 7/15* 7/15= 0.101

B
P(Blue and Red)+P(Red and Blue)= 7/15* 8/14 + 8/15* 7/14= 0.532