innocous wrote:
If A, B & C can build a wall in 4 hours, working together, at their respective rates. If their working rates remain the same, who among the three can build the same wall in shortest amount of time working independently?
(1) Working alone B can build the same wall in more than eight but less than eleven days.
(2) Working together B and C can build the same wall in five days.
I think there is a typo mistake in a question --- It has to be 4 days in the question and not 4 hours for the answer to be E.
Otherwise the answer would be B undoubtedly.
Bunuel Could you please look into this question once?
Anyways considering the question be 4 days, then
The more the rate of any individual the less time it takes to build the wall independently. Since Time is inversely proportional to Rate.
Question stem gives us 1 equation. Let A,B,C be the rates of the individuals.
Then \(Work = Rate * Time\)
Therefore Assuming Work to be done is 40 units.
Then \(40 = (A+B+C)*4\). Therefore \(A+B+C = 10 units/day\)
Therefore \(A+B+C = 10\)
Statement 1 :- \(11 > Time taken by B > 8\)
Therefore Rate of B will be \(\frac{40}{11} < B < \frac{40}{8}\)
Note :- (Inequalities change since T and R are inversely proportional. Also Considering Work as 40 units as did before)that will be \(3.66 < B < 5\)
Now considering \(B = 3.7\)
\(A+C = 10 - 3.7 = 6.3\)
Therefore A can be 5.3 and C can be 1 (A will be the fastest)
Again considering B = 4.9 Then A+C = 5.1 (A can be 4.1 and C can be 1) --- B will be fastest
Hence 2 answers --- Not sufficient
Statement 2 :-
Time taken by B and C together is 5 days
Then
\(B+C = 40/5 = 8 units/day\)
Therefore A = 2 and B can be 3, C can be 5 --- C will be fastest
And A = 2 and B can be 5, C can be 3 ---- B will be fastest
Hence insufficient
Considering both the statements :-
\(A = 2; 3.66<b<5\)
a) A = 2; B = 3.7; C = 4.3 ---- C will be fastest
b) A = 2; B = 4.9; C = 3.1 ---- B will be fastest
Still not sufficient..
Hence Answer is E
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