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# GMAT: Math 39

195-197, pgs. 178-179. Created by Sal Khan.

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• question 197. I also got 50%. But i just kicked out the 20% and calculated the intersection of set q1 and q2. Did i just get luck or is this a viable appproach?
• I'm a little bit confused by 196, they say the ratio is doubled, but in fact it has been reduced.

I'll take the example of s : a, where it is 2 : 50 = 1 : 25.

In order for you to double this ratio, it would have to be 1 : 50. For every soap, you now have 50 alcohol.

If you multiple it by 2, you get.... 1 : 12.5, which has reduced the soap to alcohol ratio by 2x.

Have I interpreted the question wrong?
• Think of it as a fraction s/a = 2/50 ... if you were to double the fraction you would get 4/50 = (2/50)*2.

Your approach => would double the ratio of a:s ... the language is important!
• Question 195. Is there a way to solve the problem, using formulas? Thank you!
• It is Pascal's Triangle. The n-th diagonal from top-left to bottom-right will contain the same numbers as the n-th row of Pascal's Triangle (1; 1,1; 1,2,1; 1,3,3,1; 1,4,6,4,1), which is also the coefficients of the binomial (a+b)^n.
It can also be written as a combinatorial statement, "n choose k" (of n objects, choose k of them; in how many different ways can they be chosen?).
http://en.wikipedia.org/wiki/Pascal%27s_triangle
• 196. still not sure why 0 is changed to 0. why not keep it at 0?
• To keep the s:a:w more manageable.

if you know and 0 its more difficult to compare the 50 and 100
(1 vote)
• 11/20 as a percent on math grid
(1 vote)
• Two angles in a triangle are 54 angle and 72 angle. Find the ratio of the third angle to the sum of the first two?
(1 vote)
• since sum of the three angles in a triangle is 180,the third angle is 54
and the ratio is 3:7
(1 vote)
• What kind of problem is 195? Where else could I find variations of this?
(1 vote)
• In a certain Venn diagram problem the following information is given: "100 people were asked whether they had ever owned cats ___ dogs as pets. 57 people said they had cats or dogs." Carefi;;u ex[plain exactly what the statement means if the blank is filled in with and or or.
(1 vote)