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Two varieties of steel, A and B, have a ratio of iron to chromium as 5
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24 May 2015, 09:03
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Two varieties of steel, A and B, have a ratio of iron to chromium as 5:1 and 7:2, respectively. Steel C is produced by mixing alloys A and B at a ratio of 3:2. What is the ratio of iron to chromium in C? (A) 17 : 73 (B) 78 : 14 (C) 45 : 30 (D) 73 : 17 (E) 4 : 9
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Re: Two varieties of steel, A and B, have a ratio of iron to chromium as 5
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24 May 2015, 09:35
In 6 parts of alloy A, 5 parts are iron, and 1 part is chromium. In 9 parts of alloy B, 7 parts are iron and 2 parts are chromium. First, to compare the two alloys, get the same number of parts in total  we can use 18. So we have: In 18 parts of alloy A, 15 parts are iron and 3 are chromium. In 18 parts of alloy B, 14 parts are iron and 4 are chromium. So combining 3 of A with 2 of B, we'd be combining 45 and 28 parts of iron, or 73 parts of iron, with 9 and 8 of chromium, or 17 of chromium, so 73 to 17 is the answer.
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Re: Two varieties of steel, A and B, have a ratio of iron to chromium as 5
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23 Apr 2016, 04:33
Finding the weighted average of one of the two : Iron: In solution A iron is 5/6 In solution B iron is 7/9 The ratio for Solution C is 3:2 for A and B respectively. This means that 60% of A was used and 40% of B To find the weight of iron in the new solution: we do the weighted average: \(\frac{5}{6}*\frac{3}{5}+\frac{7}{9}*\frac{2}{5}\) We get \(\frac{73}{90}\) 73 is the weight of Iron and 90 is total
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Re: Two varieties of steel, A and B, have a ratio of iron to chromium as 5
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24 May 2015, 12:12
naeln wrote: Two varieties of steel, A and B, have a ratio of iron to chromium as 5:1 and 7:2, respectively. Steel C is produced by mixing alloys A and B at a ratio of 3:2. What is the ratio of iron to chromium in C?
(A) 17 : 73 (B) 78 : 14 (C) 45 : 30 (D) 73 : 17 (E) 4 : 9
Could any one please help me understand how to go about this type of questions?
Thank you in advance. Such questions test your knowledge on weighted average concept . Initially this technique may seem daunting but once you get familiar , you will find this technique very useful on GMAT. Ok , so for this question we can focus on either Iron or chromium to get to the solution . i will show both ways . in A , Iron = 5/6 in B , Iron= 7/9 resultant mixture has 3 portions of A for every 2 portions of B , so weighted average of Iron will lie closer to A than to B . Specifically , w.Avg (Iron) in mixture will be 2 portion away from A and 3 portion away from B as shown in picture.
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Re: Two varieties of steel, A and B, have a ratio of iron to chromium as 5
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08 Apr 2016, 11:50
iron in 3A+2B=3(5/6)+2(7/9)=73/18 chromium in 3A+2B=3(1/6)+2(2/9)=17/18 iron:chromium ratio in C=(73/18)/(17/18)=73/17



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Re: Two varieties of steel, A and B, have a ratio of iron to chromium as 5
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29 Sep 2018, 10:30
Combine the 2 alloys in the given ratio. We get (3(5/6)+2(7/9))/(3(1/6)+2(2/9))=>(5/2+14/9)/(1/2+4/9)=>73/17 choice D
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Re: Two varieties of steel, A and B, have a ratio of iron to chromium as 5
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20 Apr 2019, 01:50
reasoning: we have a ratio I:C of group A and a different ratio of I:C for group B. We are given the ratio at which A and B are used to form a third group C (these are the weights). Then we are asked about the ratio of I:C of this latest group C.
what % of I do we have in A? And, how will be reflected this distribution (%) of A in group C?
(5/6)*3
what % of I do we have in I? And, how will be reflected this distribution (%) of B in group C?
(7/9)*2
Then, we apply the same reasoning for Chromium, and we end up having the following equation:
For I: (5/6)*3+(7/9)*2 For Chromium: (1/6)*3+(2/9)*2
Total Weighted Avg. ratio to get the ratio of I/C in group C:
(5/6)*3+(7/9)*2 73  =  (1/6)*3+(2/9)*2 17



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Two varieties of steel, A and B, have a ratio of iron to chromium as 5
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21 Apr 2019, 03:07
naeln wrote: Two varieties of steel, A and B, have a ratio of iron to chromium as 5:1 and 7:2, respectively. Steel C is produced by mixing alloys A and B at a ratio of 3:2. What is the ratio of iron to chromium in C?
(A) 17 : 73 (B) 78 : 14 (C) 45 : 30 (D) 73 : 17 (E) 4 : 9 Intuitive Representationvariables > Iron  Chromium  Total Truth 1 > 5x  x  6x Truth 2 > 7y  2y  9y Truth 3 > 3*5x  3*x   18x Truth 3 > 2*7y  2*2y  18y what connections can we make?6x=9y => x=3y/2 Iron = 3*5x+ 2*7y = 36.5y, chromium= 3*x+2*2y=8.5y => Iron:chromium = 73:17
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Re: Two varieties of steel, A and B, have a ratio of iron to chromium as 5
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21 Apr 2019, 03:45
Using Alligation to knock out this one :
Lets take the Iron part :
[5][/6] [7][/9]
x 3 2
This simplifies to : [79x][/6x5] = [9][/4] which boils down to x = [73][/90]
But remember we started with part to the whole so the above is the expression for Iron to whole ( in C) Therefore the desired ratio will be : [73][/9073]= [73][/17], which is D




Re: Two varieties of steel, A and B, have a ratio of iron to chromium as 5
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21 Apr 2019, 03:45






