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IMO 7.5. Agree with tarkumar A can do the job in 12 days. B 60% better 1/12*1.6=1/12*160/100=2/15 Days for B will be 1/(2/15)=15/2=7.5

This question is from OG 11. The diagram in some books is incorrect. E is less then 2. So the answer is A.

gmatrookie1, Here are the steps. 25*10^(-4)*25*10(-3)*25*10(-5)*2^(k)=n 25^(3)*10^(-12)*2^(k)=n 25^(3)*2^(-12)*5^(-12)*2^(k)=n 5^(6)*2^(-12)*5^(-12)*2^(k)=n 5^(-6)*2^(-12)*2^(k)=n 2^k/(5^6*2^12)=n Let me know if you have more questions.

Agree with above. Solved the same way. 16000/PI

Agree with B. Same way as explained by venkat007

Number of ways the cars can be arranged ia 5*4*3*2*1/3*2=20

Area of circle = (Pi)R^2 So, (Pi)R^2=24(PI) R=Sqrt 24 Perimiter of circle is 2(Pi)R Perimiter of Semi Circle will be 2(PI)R +2R(or Diameter) SO we have 2 (PI) sq rt 24 + 2sqrt24 or 4sqrt6 + 2sqrt6(pie) Second problem is the same concept. The thing here to remember is that the diameter will also be part of the perimiter of a Semi Circle. Let me know if you have any more questions

Agree with A. Same approach as above. Total rats 100. 50 died 15-male 35-female m rate =15/40 female rate 35/60 m/f rate= 9/14

Agree with 72/Pi. 2 PI R=72 2R=72/PI

Agree with E. I used the plug and play method as Dude suggested.

Just wanted to add, that I did not perform the last step in the SD calcs of taking the SQ root of 8. In this case its not important.

Adree with 2/5. Total poss 5 and fav are 2. thus 2/5. Thx Krovvidy

Agree with 20

Gmatcraze, basically what we are trying to do is add 2 more numbers to the set and keep the new SD close to the original SD. So, first things first, find the original SD. Mean =4, then thake the diff between all the numbers in the set and the mean. 0-4=4 2-4=2 4-4=0 6-4=2 8-4=4 Then, SQ each one and add them you will get 40 (4^2+2^2+0^0+2^2+4^2=40). The SD is the avg of these numbers so 40/5=8. Original SD = sq rt 8. Now, we are looking for 2 numbers, when added to 40 and divided by 7 (because we add 2 new numbers to the original 5) will give us a new SD closest to the original sq rt 8. Pick 2 numbers from the choices. Lets say 2&6 (d) 2-4(mean)=2 6-4=2 2^2+2^2=8 40+8=48 48/7 is a little less then 7. As you do this with the other choices as sachin_kapoor shows below, you will see that this is the best choice as it is closest to 8. Make sence? Let me know if you need more info.

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