Search found 4 matches
Here it's best to calculate the probability that 0, 1, or 6 heads appear and subtract that from 1. One of the benefits of this approach is that you only have to calculate the probability of 3 results rather than 4 results (2, 3, 4, or 5 heads). But the real payoff is the simplicity of the calculatio...
- by John@GMATPrepNow
Tue Jun 02, 2015 10:15 pm- Forum: Problem Solving
- Topic: Probability and Permutation problem
- Replies: 2
- Views: 1187
Another Method: Pascal's Triangle (Challenge problem included) http://s12.postimg.org/pyzstyizd/Pascal_s_Traingle.jpg We can use Pascal's triangle to calculate combinations. For instance, if we need to calculate 5C2, we count down to the 6th row, and find the 3rd entry - 10. If we need to calculate ...
- by John@GMATPrepNow
Tue Jun 02, 2015 6:46 pm- Forum: Problem Solving
- Topic: In how many ways can a room be illuminated if there are 7
- Replies: 8
- Views: 5570
"sqrt(576) = 24" is a bad answer because the average test taker does not have that memorized. ManifestDestiny88 - I think you are correct. The average test taker wouldn't know that the square root of 576 is 24, but who wants to be the average test taker!? I have all my students memorize s...
- by John@GMATPrepNow
Sat May 30, 2015 12:56 pm- Forum: Problem Solving
- Topic: Radicals: sqrt((16)(20)+ ( 8 ) (32))
- Replies: 11
- Views: 9921
RadiumBall wrote: If P, Q, R, and S are positive integers, and P/Q=R/S , is R divisible by 5 ? (1) P is divisible by 140 (2) Q = 7^x , where x is a positive integer We can rephrase by rewriting the formula as PS = QR, and writing the question as R = 5K where K is an integer. (1) If P is divisible b...
- by John@GMATPrepNow
Sat May 30, 2015 10:05 am- Forum: Data Sufficiency
- Topic: Divisibility Problem
- Replies: 6
- Views: 2402