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# Robin mixes two liquids, one blue in colour and other red in

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Current Student
Joined: 22 Jul 2014
Posts: 123
Concentration: General Management, Finance
GMAT 1: 670 Q48 V34
WE: Engineering (Energy and Utilities)
Robin mixes two liquids, one blue in colour and other red in  [#permalink]

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26 Aug 2014, 23:24
2
10
00:00

Difficulty:

75% (hard)

Question Stats:

61% (02:42) correct 39% (03:20) wrong based on 191 sessions

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Robin mixes two liquids, one blue in colour and other red in colour in the ratio 3:1 and sells the mixture at the rate of $15 per litre, thereby making a 20% profit on his outlay. The blue liquid costs Robin$2 per litre lesser than the red liquid. How much does a litre of red liquid cost?

A) $14 B)$13
C) $12 D)$11
E) $10 Source: 4Gmat Hi can someone share strategies and concepts on Ratios, Mixtures and Propotion ##### Most Helpful Community Reply Current Student Status: It always seems impossible until it's done!! Joined: 29 Aug 2012 Posts: 1124 Location: India WE: General Management (Aerospace and Defense) Robin mixes two liquids, one blue in colour and other red in [#permalink] ### Show Tags 27 Aug 2014, 00:51 5 1 In mixture problem always try to make an equation, Questions says Robin sells the 1 litre of mixture for$15.

The ratio given is 3:1 for Blue: Red.

Let the multiplier for ratio be 1--(take small and simple terms which is easy for calculation or multiple of 10.

So we have 3 litre of blue liquid and 1 litre of red liquid. So total of 4 litre,

Robin sells 4 litre of mixture for=4* 15= $60 We know that Blue cost$2 less than the red per litre.

So B= R-2 per litre.

here we have 3 litre of blue= $$3(R-2)$$

Now since the question says he gets 20% profit. The equation will be,

$$[3(R-2)+ R] + \frac{20}{100} [3(R-2)+ R]= 60.$$

On simplifying,

$$1.2[3R-6+R]= 60$$

$$1.2(4R-6)=60$$

$$4R- 6= 50$$.

$$4R= 56$$

$$R= 56/4= 14$$

The answer is A. Hope it helps

_________________
##### General Discussion
Intern
Joined: 27 Aug 2014
Posts: 27
GMAT Date: 09-27-2014
Robin mixes two liquids, one blue in colour and other red in  [#permalink]

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28 Aug 2014, 03:26
1
1
Alternative Same approach as above but finding total cost first makes it easier:

Let x be the required cost per litre of red paint.

Take 4 litres of this mixture.

Sold at 60 with a profit of 1/5th of total cost. So, total cost will be 1/6th less than 60; total cost = 50.

3(x-2) + 1(x) = 50

x = 14
Director
Joined: 23 Jan 2013
Posts: 568
Schools: Cambridge'16
Robin mixes two liquids, one blue in colour and other red in  [#permalink]

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13 Sep 2015, 23:33
B : R = 3 : 1
Cost of Red = x
Cost of Blue= x-2
What is the x?

Cost of mixture =(100/120)*15 => 12.5 dollars

0.75(x-2)+0.25x=12.5 => x=14

A
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Joined: 17 Jul 2014
Posts: 2621
Location: United States (IL)
Concentration: Finance, Economics
GMAT 1: 650 Q49 V30
GPA: 3.92
WE: General Management (Transportation)
Re: Robin mixes two liquids, one blue in colour and other red in  [#permalink]

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11 Jan 2016, 18:23
since we have 3/1 B/R, we can assume we have 4 liters in total. thus, 60$/total sold. 60=1.2x, where x is the cost, and 1.2 is the revenue. thus, x=60*10/12 = 50. now, 3B+R=50. B=R-2. substitute: 3(R-2)+R=50 3R-6+R=50 4R=56 R=56/4 R=14. A. VP Joined: 07 Dec 2014 Posts: 1128 Re: Robin mixes two liquids, one blue in colour and other red in [#permalink] ### Show Tags 25 Nov 2017, 14:25 alphonsa wrote: Robin mixes two liquids, one blue in colour and other red in colour in the ratio 3:1 and sells the mixture at the rate of$15 per litre, thereby making a 20% profit on his outlay. The blue liquid costs Robin $2 per litre lesser than the red liquid. How much does a litre of red liquid cost? A)$14
B) $13 C)$12
D) $11 E)$10

cost of liter of red liquid=c
total cost=3(c-2)+c=4c-6
total revenue=4*15=$60 1.2*(4c-6)=60 c=$14
A
Re: Robin mixes two liquids, one blue in colour and other red in &nbs [#permalink] 25 Nov 2017, 14:25
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