An armys recruitment process included n rounds of selection tasks. Fo

Question

An army’s recruitment process included n rounds of selection tasks. For the first a rounds, the rejection percentage was 60 percent per round. For the next b rounds, the rejection percentage was 50 percent per round and for the remaining rounds, the selection percentage was 70 percent per round. If there were 100,000 people who applied for the army and 1,400 were finally selected, what was the value of n?

A) 4
B) 5
C) 6
D) 8
E) 10

A) 4
B) 5
C) 6
D) 8
E) 10

chetan2u · Answer

Hi 
selected person =  \frac{4}{10}^a*\frac{1}{2}^b*\frac{7}{10}^c*100000=1400 
.. =  \frac{4}{10}^a*\frac{1}{2}^b*\frac{7}{10}^c=\frac{14}{1000} ...
If you compare left and right side, there is one 7 on each side, so c=1...

\frac{4}{10}^a*\frac{1}{2}^b=\frac{2}{100} ...
There is 100 on RHS and 20 on LHS..., So a =2...
 \frac{1}{2}^b=\frac{2}{100}*\frac{100}{16}=\frac{1}{8} 
So b=3..
Total rounds=a+b+c=2+3+1=6
C

nishantt7 · Answer

We can judge that there should be a multiplication between 7 and 2 to get 14, accordingly we can start off from the options.
Lets start with B.
Reduce 100,000 by 60%=40,000
Reduce 40,000 by 60%=16000
Reduce 16,000 by 50%=8000
reduce 8000 by 50%=4000
reduce 4000 by 50%=2000...Option B is gone
70% of 2000=1400...Answer is option C

bumpbot · Answer

Automated notice from GMAT Club BumpBot: 

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

 This post was generated automatically.

An armys recruitment process included n rounds of selection tasks. Fo

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards