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# In a laboratory, three containers, A, B and C, have equal volumes of

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Manager
Joined: 18 Jul 2019
Posts: 54
In a laboratory, three containers, A, B and C, have equal volumes of  [#permalink]

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25 Nov 2019, 01:46
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Difficulty:

75% (hard)

Question Stats:

46% (03:25) correct 54% (03:32) wrong based on 26 sessions

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In a laboratory, three containers, A, B and C, have equal volumes of different mixtures of liquid oxygen and liquid nitrogen. The concentration (by volume) of liquid oxygen in the three mixtures is 20%, 40% and 80% respectively. First, one-fifth of the contents of A are poured into B and then two-fifths of the contents of B are poured into C. The final concentration (by volume) of liquid oxygen in C is approximately

(A) 61.7%
(B) 62.4%
(C) 65.9%
(D) 68.6%
(E) 78.9%
Director
Joined: 27 May 2012
Posts: 947
In a laboratory, three containers, A, B and C, have equal volumes of  [#permalink]

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25 Nov 2019, 05:13
CaptainLevi wrote:
In a laboratory, three containers, A, B and C, have equal volumes of different mixtures of liquid oxygen and liquid nitrogen. The concentration (by volume) of liquid oxygen in the three mixtures is 20%, 40% and 80% respectively. First, one-fifth of the contents of A are poured into B and then two-fifths of the contents of B are poured into C. The final concentration (by volume) of liquid oxygen in C is approximately

(A) 61.7%
(B) 62.4%
(C) 65.9%
(D) 68.6%
(E) 78.9%

Let the 3 containers contain 100L each then Liquid Qxygen is 20L, 40L and 80L respectively. ( Note: We are asked for approximate concentration.)

When one -fifth of the contents of A are poured into B:
$$\frac{1}{5}*100$$=20L from A is put into B then B has 120L total solution and Liquid oxygen = 40+ $$\frac{20}{100}$$*20=44, Therefore concentration of LO in B becomes $$\frac{44}{120}$$.

When Two-fifths of the contents of B are poured into C:
Now $$\frac{2}{5}*120$$ =48 and $$\frac{44}{120}*48$$=17.6 Thus when 48L from B is added to C then in C we have total of 148L and LO of 80+17.6$$\approx$$98. Hence final LO concentration in $$C =\frac{98}{148}*100=$$66.21 , actual concentration will be little less than 66.21 since we took 17.6 to be 18, hence little less than 66.21 among the answer choices =65.9

Ans- C
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- Stne
In a laboratory, three containers, A, B and C, have equal volumes of   [#permalink] 25 Nov 2019, 05:13
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