Search found 80 matches
- by billzhao
Sat Feb 21, 2009 7:45 pm- Forum: Data Sufficiency
- Topic: Median and Mean problem
- Replies: 1
- Views: 1153
Remainder problem
If n is a positive integer and r is the remainder when (n-1)(n+1) is divided by 24, what is the value of r?
(1) r is not divisible by 2
(2) r is not divisible by 3
Appreciate explanations. Thanks.
- by billzhao
Sat Feb 21, 2009 7:33 pm- Forum: Data Sufficiency
- Topic: Remainder problem
- Replies: 2
- Views: 1408
The probability ofchoosing the first sibling is 4/9 and the probability of choosing the second sibling is 1/8.
So the probability of choosing a sibling pair is 4/9*1/8=1/18
So the probability of not choosing a sibling pair is 1-1/18=17/18
What is OA?
- by billzhao
Sat Feb 21, 2009 3:51 am- Forum: Problem Solving
- Topic: The lesson is 'never try'
- Replies: 1
- Views: 1280
The number of 4-digit integers that do not contain 3 is 8*9^3 The number of 4-digit integers that do not contain 6 is 8*9^3 The number of 4-digit integers that do not contain 3 and 6 is 7*8^3 Billzhao , why did you take 8*9^3 actually it is 9 * 9 * 9 * 9 plz don't misunderstand me I am bit weak in ...
- by billzhao
Fri Feb 20, 2009 5:00 am- Forum: Problem Solving
- Topic: help with permutation problem!
- Replies: 6
- Views: 1490
Re: tossed 10 times
A fair coin is tossed 10 times. What is the probability that two heads do not occur consecutively? (A) 1/ 2^4 (B) 1/2^3 (C)1/2^5 (D) None of the above (E) It cannot be determined by the information provided The answer is 1/2+1/2^10. The probability that two heads occur consecutively = (1/2)^2+(1/2)...
- by billzhao
Fri Feb 20, 2009 4:18 am- Forum: Problem Solving
- Topic: tossed 10 times
- Replies: 8
- Views: 2447
Re: A 750+ treat
Three fair coins are labeled with a zero (0) on one side and a one (1) on the other side. Jimmy flips all three coins at once and computes the sum of the numbers displayed. He does this over 1000 times, writing down the sums in a long list. What is the expected standard deviation of the sums on thi...
- by billzhao
Fri Feb 20, 2009 4:02 am- Forum: Problem Solving
- Topic: A 750+ treat
- Replies: 14
- Views: 2849
To solve this, first realize that you don’t need to do calculations for day one; the odds of him wearing any outfit are 1. For day two, he needs to wear one of the two other shirts that he didn’t wear on day one, the same pair of shoes, and one of the two other pants; the probability of this is: 2/3...
- by billzhao
Thu Feb 19, 2009 8:43 pm- Forum: Problem Solving
- Topic: a probability problem, who can help? Thanks!
- Replies: 5
- Views: 1359
Students and Subjects problem
A certain college has a total of 400 seniors, each majoring in exactly one of six subjects. A minimum of 20 seniors major in each of the six subjects. If three-quarters of the seniors major in one of four subjects, what is the greatest possible number of seniors majoring in one of the other two subj...
- by billzhao
Wed Feb 18, 2009 5:25 pm- Forum: Problem Solving
- Topic: Students and Subjects problem
- Replies: 7
- Views: 1737
a probability problem, who can help? Thanks!
A man chooses an outfit from 3 different shirts, 2 different pairs of shoes, and 3 different pants. If he randomly selects 1 shirt, 1 pair of shoes, and 1 pair of pants each morning for 3 days, what is the probability that he wears the same pair of shoes each day, but that no other piece of clothing...
- by billzhao
Wed Feb 18, 2009 5:01 pm- Forum: Problem Solving
- Topic: a probability problem, who can help? Thanks!
- Replies: 5
- Views: 1359
Ra=1/20, Rb=1/30
(Ra+Rb)*(t-10)+Rb*10=1 =>
(1/20+1/30)*(t-10)+1/30*10=1
We can solve the equation for t.
t=18
- by billzhao
Wed Feb 18, 2009 7:02 am- Forum: Problem Solving
- Topic: A quits before the project is completed
- Replies: 40
- Views: 23885
- by billzhao
Wed Feb 18, 2009 6:52 am- Forum: Problem Solving
- Topic: 9 consecutive integers that start with m + 2
- Replies: 5
- Views: 5770
Re: Work Problem
Whats the next step I know the formula is 1/t1 + 1/t2 = 1/t t=total hours or days I guess of both people working. Clarissa and Shawna working together can paint the exterior of a house in 6 days. Clarissa by herself can complete this job in 5 days less than Shawna. How long will it take Clarissa to...
- by billzhao
Wed Feb 18, 2009 6:47 am- Forum: Problem Solving
- Topic: Work Problem
- Replies: 3
- Views: 2455
This question asks us to find the sum of a series with the first item: a1=101, last item: an=998and tolerance: d=3
first, we need to find n:
an=a1+d*(n-1)
998=101+3*(n-1) =>n=300
Sn=(a1+an)*n/2=(101+998)*300/2=164,850
- by billzhao
Wed Feb 18, 2009 6:30 am- Forum: Problem Solving
- Topic: What is the sum?
- Replies: 4
- Views: 1320
mjjking, I guess i need to explain the relationship of the three sets. I have drawn the graph for explanation.
- by billzhao
Wed Feb 18, 2009 5:57 am- Forum: Problem Solving
- Topic: help with permutation problem!
- Replies: 6
- Views: 1490
Re: ims quant
a certain amount was to be divided among A, B and C in the ratio of 4:5:6 but by mistake, it was divided in such a manner that 4 time of A's share was equal to 5 times of B's share and 6 times of C's share. as a result A got $154 more than the excepted amount . what was the amount that was divided ...
- by billzhao
Wed Feb 18, 2009 3:03 am- Forum: Problem Solving
- Topic: ims quant
- Replies: 4
- Views: 1881