Search found 23 matches
Yes, this is a tough question, IMO definitely in the 700+ category. The question here is structured to require us to compute at different levels and integrate. There doesn't appear to be any (easier) way to avoid the probability computations. Practice will help improve timing - review other probabil...
- by Jim@Knewton
Tue Aug 02, 2011 4:45 pm- Forum: Problem Solving
- Topic: tough combination
- Replies: 8
- Views: 3652
On a related note ,can anybody say , in how many ways one can put 3 letters in 3 envelopes? 3 unique letters in 3 unique address envelopes: (3*3)*(2*2)*(1*1) = 36 possible sequence ordered arrangements (like cards on a table) (3*3)= 3L for each of 3E,(2*2)=2L for each of 2E and (1*1)= 1L for 1E If ...
- by Jim@Knewton
Sun Jul 31, 2011 12:45 pm- Forum: Problem Solving
- Topic: letter and envelope
- Replies: 21
- Views: 27741
In addition to the excellent posts above, here is some food for thought: Note the wording of the question: "A fair die is rolled once and a fair coin is flipped once. What is the probability that either the die will land on 3 or that the coin will land on heads?" Especially " either ...
- by Jim@Knewton
Sat Jul 30, 2011 8:53 pm- Forum: Problem Solving
- Topic: Probability Man Guide
- Replies: 4
- Views: 1946
Source of Q? All details correct? 1. Diff of speed = 8 mph, diff of distance = 50+16 =66 miles, => time taken = 66/8 = 8.25 hours 2. D = speed *time, let time =t, then D= 52t for B and D+50+16 = 60t for A => 8t = 66, so t=8.25 3. Every hour A gains 8 miles on B => For given answer choices in hours: ...
- by Jim@Knewton
Sat Jul 30, 2011 12:47 pm- Forum: Problem Solving
- Topic: Motion Problem!!
- Replies: 4
- Views: 1610
Good question Ruplun :!: As with most other probability questions, there are a variety of ways to solve this, and here are a few: 1. The best and the easiest has been posted above by ColumbiaVC :!: (and Tryingtobeat :!:): 9c4/12c4 = 126/495 = [spoiler]14/55 = 0.254545[/spoiler] where 9c4 = ways to s...
- by Jim@Knewton
Sat Jul 30, 2011 12:16 pm- Forum: Problem Solving
- Topic: children not selected
- Replies: 8
- Views: 1760
Interesting question Neya! "discharge a debt" = repay full principal + all interest (and, in the real world, any associated frictional costs /fees as may apply). We can look at this in 3 parts: 1. GMAT solution (shoot from the hip) 2. Financial modeling (a bit of it) for simple interest 3....
- by Jim@Knewton
Sat Jul 16, 2011 12:26 am- Forum: Problem Solving
- Topic: Simple Interest
- Replies: 2
- Views: 7643
By definition: H(100) = (2*4*6*…..*98 *100) ----(50 even terms within the parenthesis) = > H(100) = 2^50(1*2*3*4….*49*50) ----(factoring 2 from each of the 50 even terms) Thus H(100) is divisible by all primes between 1 & 50 => H(100)+1 = 2^50(1*2*3*4….*49*50) + 1 1 is not evenly divisible...
- by Jim@Knewton
Fri Jul 15, 2011 10:09 pm- Forum: Problem Solving
- Topic: Factorial and primes
- Replies: 2
- Views: 1515
Certain DS questions are (over)loaded with words! In cases like this it is best to start with the Q stem:3 < m < 13 < n => m could be any of(4,5,6,7,8,9,10,11 or 12) => To conclude on the possibility of equal assignment of n to m rooms, n must be conclusively shown to be a multiple of m (of ALL pos...
- by Jim@Knewton
Wed Jul 13, 2011 8:28 am- Forum: Data Sufficiency
- Topic: OG DS Q128
- Replies: 2
- Views: 1224
Very interesting question Mariah! Please see the image (solution structure) below to review along with the explanation. The solution can be structured in 7 'selection conditions' (SC 1 to SC 7) SC1: All five Ls (letters) are the same Only possible for "A" = 1 letter => Number of ways = 1C1...
- by Jim@Knewton
Thu Jul 07, 2011 10:52 pm- Forum: Problem Solving
- Topic: tough combination
- Replies: 8
- Views: 3652
Let 1 shot = s (quantity)
=> New mix overall quantity = 2s + 3s = 5s
=> New mix alcohol quantity = 0.15*2s + 0.20*3s = 0.9s
=> New content [spoiler]= 0.9s/5s = 0.18 = 18%[/spoiler] alcohol
- by Jim@Knewton
Wed Jul 06, 2011 10:40 pm- Forum: Problem Solving
- Topic: averages
- Replies: 3
- Views: 1107
Pr| K selected = 1/3 Pr| K not selected = 2/3 Pr| M selected = 1/5 Pr| M not selected = 4/5 Quickest method (Recommended): Pr| Only one selected = (K selected)*(M not selected) + (M selected)*(K not selected) => Pr| Only one selected = (1/3)* (4/5) + (1/5)*(2/3) = [spoiler]6/15 = 2/5[/spoiler] Alter...
- by Jim@Knewton
Tue Jul 05, 2011 5:44 pm- Forum: Problem Solving
- Topic: Probability Problem
- Replies: 4
- Views: 2736
Thank you mbacult - just edited the typo!
...and gmatblood, I thought you posted the OA -that would be the case if:
0.5(x^2) - 1.4x + 0.7 for x = 1.4
=> 0.5*(1.4^2) - (1.4^2) + 0.7
=> -0.5*(1.4^2)+ 0.7 ..........but -0.5*(1.4^2) = - (1.4)*0.7
=> -0.7*(1.4-1)
=> -0.28
for the +0.7
- by Jim@Knewton
Tue Jul 05, 2011 4:59 pm- Forum: Problem Solving
- Topic: what is the value!
- Replies: 7
- Views: 1519
0.5(x^2) - 1.4x - 0.7 for x = 1.4 => 0.5*(1.4^2) - (1.4^2) - 0.7 => -0.5*(1.4^2)- 0.7 ..........but -0.5*(1.4^2) = - (1.4)*0.7 => -0.7*(1.4+1) [spoiler] => -1.68 Hence E[/spoiler] In such questions, usually look for a way to solve rather than compute - computations can be time consuming and comparat...
- by Jim@Knewton
Tue Jul 05, 2011 2:11 pm- Forum: Problem Solving
- Topic: what is the value!
- Replies: 7
- Views: 1519
Brilliant Frank! ...and Ozlemg, here is a here is a methodical quickie: Let time(for Hui) to meet / overtake = t hours Then Feng time = t hr + 30 minutes = (t + 0.5) hrs Feng Distance = 6*(t+0.5) = 6t + 3 and Hui Distance = 7*t => 7t = 6t + 3 => t = 3 This method will help even if the numbers / ques...
- by Jim@Knewton
Mon Jul 04, 2011 7:46 pm- Forum: Problem Solving
- Topic: racing problem!
- Replies: 4
- Views: 1677
The question appears to be erroneous / incomplete / answer choices are wrong - what is the source of this question? As is, the answer should be: 461 possible ways to select a com. of 5 with at least 1 g from 5 bs and 6 gs. BUT if you edit the question to read: "A committee of 5 is to be selecte...
- by Jim@Knewton
Mon Jul 04, 2011 6:44 pm- Forum: Problem Solving
- Topic: Permutations and Combinations - doubt
- Replies: 3
- Views: 1657